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	$133.36	12.578%	$150.134	$150.13	$150.15	$150.10
Purchase #2	$10.42	4.242%	$10.862	$10.86	$10.85	$10.90
Purchase #3	$241.33	11.756%	$269.7008	$269.70	$269.70	$269.70
Purchase #4	$246.37	3.346%	$254.6135	$254.61	$254.60	$254.60
Purchase #5	$6.77	8.689%	$7.3582	$7.36	$7.35	$7.40
Purchase #6	$235.86	4.743%	$247.0468	$247.05	$247.05	$247.00
Purchase #7	$33.46	13.211%	$37.8804	$37.88	$37.90	$37.90
7 purchase totals =	$907.57		$977.5957	$977.59	$977.60	$977.60