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	$99.67	11.535%	$111.1669	$111.17	$111.15	$111.20
Purchase #2	$216.75	11.756%	$242.2311	$242.23	$242.25	$242.20
Purchase #3	$13.83	7.722%	$14.898	$14.90	$14.90	$14.90
Purchase #4	$147.37	5.772%	$155.8762	$155.88	$155.90	$155.90
Purchase #5	$49.26	4.690%	$51.5703	$51.57	$51.55	$51.60
Purchase #6	$10.65	10.143%	$11.7302	$11.73	$11.75	$11.70
Purchase #7	$190.53	13.404%	$216.0686	$216.07	$216.05	$216.10
7 purchase totals =	$728.06		$803.5413	$803.55	$803.55	$803.60