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	$169.73	6.320%	$180.4569	$180.46	$180.45	$180.50
Purchase #2	$22.83	11.319%	$25.4141	$25.41	$25.40	$25.40
Purchase #3	$89.62	9.231%	$97.8928	$97.89	$97.90	$97.90
Purchase #4	$160.42	11.521%	$178.902	$178.90	$178.90	$178.90
Purchase #5	$73.77	12.710%	$83.1462	$83.15	$83.15	$83.10
Purchase #6	$244.41	12.603%	$275.213	$275.21	$275.20	$275.20
Purchase #7	$113.60	12.530%	$127.8341	$127.83	$127.85	$127.80
7 purchase totals =	$874.38		$968.8591	$968.85	$968.85	$968.80