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	$164.90	5.634%	$174.1905	$174.19	$174.20	$174.20
Purchase #2	$128.82	13.596%	$146.3344	$146.33	$146.35	$146.30
Purchase #3	$192.25	8.740%	$209.0527	$209.05	$209.05	$209.10
Purchase #4	$84.77	6.312%	$90.1207	$90.12	$90.10	$90.10
Purchase #5	$196.32	4.738%	$205.6216	$205.62	$205.60	$205.60
Purchase #6	$23.36	10.730%	$25.8665	$25.87	$25.85	$25.90
Purchase #7	$218.97	5.282%	$230.536	$230.54	$230.55	$230.50
7 purchase totals =	$1,009.39		$1,081.7224	$1,081.72	$1,081.70	$1,081.70