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	$102.38	8.760%	$111.3485	$111.35	$111.35	$111.30
Purchase #2	$12.76	3.654%	$13.2263	$13.23	$13.25	$13.20
Purchase #3	$186.81	6.666%	$199.2628	$199.26	$199.25	$199.30
Purchase #4	$242.90	11.730%	$271.3922	$271.39	$271.40	$271.40
Purchase #5	$40.48	13.793%	$46.0634	$46.06	$46.05	$46.10
Purchase #6	$113.68	9.529%	$124.5126	$124.51	$124.50	$124.50
Purchase #7	$151.96	9.632%	$166.5968	$166.60	$166.60	$166.60
7 purchase totals =	$850.97		$932.4026	$932.40	$932.40	$932.40