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	$100.85	10.250%	$111.1871	$111.19	$111.20	$111.20
Purchase #2	$241.52	10.279%	$266.3458	$266.35	$266.35	$266.30
Purchase #3	$84.43	9.250%	$92.2398	$92.24	$92.25	$92.20
Purchase #4	$52.33	4.236%	$54.5467	$54.55	$54.55	$54.50
Purchase #5	$32.71	9.800%	$35.9156	$35.92	$35.90	$35.90
Purchase #6	$84.78	10.773%	$93.9133	$93.91	$93.90	$93.90
Purchase #7	$36.89	12.751%	$41.5938	$41.59	$41.60	$41.60
7 purchase totals =	$633.51		$695.7421	$695.75	$695.75	$695.60