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	$51.36	4.317%	$53.5772	$53.58	$53.60	$53.60
Purchase #2	$101.82	11.438%	$113.4662	$113.47	$113.45	$113.50
Purchase #3	$184.34	8.121%	$199.3103	$199.31	$199.30	$199.30
Purchase #4	$223.33	8.167%	$241.5694	$241.57	$241.55	$241.60
Purchase #5	$158.68	4.495%	$165.8127	$165.81	$165.80	$165.80
Purchase #6	$78.85	11.786%	$88.1433	$88.14	$88.15	$88.10
Purchase #7	$244.34	11.230%	$271.7794	$271.78	$271.80	$271.80
7 purchase totals =	$1,042.72		$1,133.6585	$1,133.66	$1,133.65	$1,133.70