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	$193.91	11.563%	$216.3318	$216.33	$216.35	$216.30
Purchase #2	$100.86	10.378%	$111.3273	$111.33	$111.35	$111.30
Purchase #3	$237.61	12.441%	$267.1711	$267.17	$267.15	$267.20
Purchase #4	$227.35	11.743%	$254.0477	$254.05	$254.05	$254.00
Purchase #5	$146.29	4.285%	$152.5585	$152.56	$152.55	$152.60
Purchase #6	$98.64	8.552%	$107.0757	$107.08	$107.10	$107.10
Purchase #7	$66.74	7.699%	$71.8783	$71.88	$71.90	$71.90
7 purchase totals =	$1,071.40		$1,180.3904	$1,180.40	$1,180.45	$1,180.40