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	$184.40	4.529%	$192.7515	$192.75	$192.75	$192.80
Purchase #2	$56.79	8.515%	$61.6257	$61.63	$61.65	$61.60
Purchase #3	$244.61	12.763%	$275.8296	$275.83	$275.85	$275.80
Purchase #4	$18.58	9.473%	$20.3401	$20.34	$20.35	$20.30
Purchase #5	$244.60	8.578%	$265.5818	$265.58	$265.60	$265.60
Purchase #6	$127.78	8.105%	$138.1366	$138.14	$138.15	$138.10
Purchase #7	$165.56	4.738%	$173.4042	$173.40	$173.40	$173.40
7 purchase totals =	$1,042.32		$1,127.6695	$1,127.67	$1,127.75	$1,127.60