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	$9.37	7.820%	$10.1027	$10.10	$10.10	$10.10
Purchase #2	$41.27	3.682%	$42.7896	$42.79	$42.80	$42.80
Purchase #3	$54.94	7.755%	$59.2006	$59.20	$59.20	$59.20
Purchase #4	$139.93	13.740%	$159.1564	$159.16	$159.15	$159.20
Purchase #5	$99.29	11.317%	$110.5266	$110.53	$110.55	$110.50
Purchase #6	$223.58	7.688%	$240.7688	$240.77	$240.75	$240.80
Purchase #7	$58.34	5.635%	$61.6275	$61.63	$61.65	$61.60
7 purchase totals =	$626.72		$684.1722	$684.18	$684.20	$684.20