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	$133.67	12.663%	$150.5966	$150.60	$150.60	$150.60
Purchase #2	$120.37	5.150%	$126.5691	$126.57	$126.55	$126.60
Purchase #3	$164.62	9.404%	$180.1009	$180.10	$180.10	$180.10
Purchase #4	$231.25	8.500%	$250.9063	$250.91	$250.90	$250.90
Purchase #5	$221.50	11.748%	$247.5218	$247.52	$247.50	$247.50
Purchase #6	$187.37	8.776%	$203.8136	$203.81	$203.80	$203.80
Purchase #7	$32.70	13.437%	$37.0939	$37.09	$37.10	$37.10
7 purchase totals =	$1,091.48		$1,196.6022	$1,196.60	$1,196.55	$1,196.60