Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.46	3.110%	$103.5843	$103.58	$103.60	$103.60
Purchase #2	$170.73	10.242%	$188.2162	$188.22	$188.20	$188.20
Purchase #3	$33.82	3.467%	$34.9925	$34.99	$35.00	$35.00
Purchase #4	$54.54	3.567%	$56.4854	$56.49	$56.50	$56.50
Purchase #5	$31.51	3.302%	$32.5505	$32.55	$32.55	$32.60
Purchase #6	$108.37	13.788%	$123.3121	$123.31	$123.30	$123.30
Purchase #7	$217.74	12.595%	$245.1644	$245.16	$245.15	$245.20
7 purchase totals =	$717.17		$784.3054	$784.30	$784.30	$784.40