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	$98.47	6.756%	$105.1226	$105.12	$105.10	$105.10
Purchase #2	$42.89	4.783%	$44.9414	$44.94	$44.95	$44.90
Purchase #3	$97.61	4.257%	$101.7653	$101.77	$101.75	$101.80
Purchase #4	$181.85	9.458%	$199.0494	$199.05	$199.05	$199.00
Purchase #5	$247.89	3.843%	$257.4164	$257.42	$257.40	$257.40
Purchase #6	$60.31	4.240%	$62.8671	$62.87	$62.85	$62.90
Purchase #7	$200.85	11.388%	$223.7228	$223.72	$223.70	$223.70
7 purchase totals =	$929.87		$994.8850	$994.89	$994.80	$994.80