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	$34.82	5.457%	$36.7201	$36.72	$36.70	$36.70
Purchase #2	$11.51	5.301%	$12.1201	$12.12	$12.10	$12.10
Purchase #3	$83.50	8.854%	$90.8931	$90.89	$90.90	$90.90
Purchase #4	$25.87	8.851%	$28.1598	$28.16	$28.15	$28.20
Purchase #5	$110.33	12.793%	$124.4445	$124.44	$124.45	$124.40
Purchase #6	$62.27	10.154%	$68.5929	$68.59	$68.60	$68.60
Purchase #7	$54.55	5.431%	$57.5126	$57.51	$57.50	$57.50
7 purchase totals =	$382.85		$418.4431	$418.43	$418.40	$418.40