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	$195.41	8.640%	$212.2934	$212.29	$212.30	$212.30
Purchase #2	$94.36	3.407%	$97.5748	$97.57	$97.55	$97.60
Purchase #3	$82.37	4.779%	$86.3065	$86.31	$86.30	$86.30
Purchase #4	$79.73	5.282%	$83.9413	$83.94	$83.95	$83.90
Purchase #5	$67.56	7.119%	$72.3696	$72.37	$72.35	$72.40
Purchase #6	$36.55	13.599%	$41.5204	$41.52	$41.50	$41.50
Purchase #7	$114.98	11.730%	$128.4672	$128.47	$128.45	$128.50
7 purchase totals =	$670.96		$722.4732	$722.47	$722.40	$722.50