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	$85.82	7.762%	$92.4813	$92.48	$92.50	$92.50
Purchase #2	$68.26	5.289%	$71.8703	$71.87	$71.85	$71.90
Purchase #3	$204.37	9.464%	$223.7116	$223.71	$223.70	$223.70
Purchase #4	$154.62	6.105%	$164.0596	$164.06	$164.05	$164.10
Purchase #5	$232.54	10.467%	$256.88	$256.88	$256.90	$256.90
Purchase #6	$48.81	13.411%	$55.3559	$55.36	$55.35	$55.40
Purchase #7	$56.69	4.760%	$59.3884	$59.39	$59.40	$59.40
7 purchase totals =	$851.11		$923.7471	$923.75	$923.75	$923.90