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	$82.73	3.416%	$85.5561	$85.56	$85.55	$85.60
Purchase #2	$128.70	8.673%	$139.8622	$139.86	$139.85	$139.90
Purchase #3	$115.80	5.146%	$121.7591	$121.76	$121.75	$121.80
Purchase #4	$53.33	3.371%	$55.1278	$55.13	$55.15	$55.10
Purchase #5	$30.41	11.571%	$33.9287	$33.93	$33.95	$33.90
Purchase #6	$59.68	12.754%	$67.2916	$67.29	$67.30	$67.30
Purchase #7	$159.54	8.819%	$173.6098	$173.61	$173.60	$173.60
7 purchase totals =	$630.19		$677.1353	$677.14	$677.15	$677.20