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	$100.54	13.638%	$114.2516	$114.25	$114.25	$114.30
Purchase #2	$202.59	13.203%	$229.338	$229.34	$229.35	$229.30
Purchase #3	$22.64	12.660%	$25.5062	$25.51	$25.50	$25.50
Purchase #4	$11.70	5.746%	$12.3723	$12.37	$12.35	$12.40
Purchase #5	$48.86	9.446%	$53.4753	$53.48	$53.50	$53.50
Purchase #6	$74.47	12.414%	$83.7147	$83.71	$83.70	$83.70
Purchase #7	$120.47	9.283%	$131.6532	$131.65	$131.65	$131.70
7 purchase totals =	$581.27		$650.3113	$650.31	$650.30	$650.40