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	$126.36	5.679%	$133.536	$133.54	$133.55	$133.50
Purchase #2	$63.26	12.280%	$71.0283	$71.03	$71.05	$71.00
Purchase #3	$134.74	3.859%	$139.9396	$139.94	$139.95	$139.90
Purchase #4	$216.84	9.118%	$236.6115	$236.61	$236.60	$236.60
Purchase #5	$157.69	4.703%	$165.1062	$165.11	$165.10	$165.10
Purchase #6	$105.62	12.537%	$118.8616	$118.86	$118.85	$118.90
Purchase #7	$136.77	11.232%	$152.132	$152.13	$152.15	$152.10
7 purchase totals =	$941.28		$1,017.2152	$1,017.22	$1,017.25	$1,017.10