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	$86.75	5.713%	$91.706	$91.71	$91.70	$91.70
Purchase #2	$168.44	10.378%	$185.9207	$185.92	$185.90	$185.90
Purchase #3	$167.64	5.117%	$176.2181	$176.22	$176.20	$176.20
Purchase #4	$244.91	12.425%	$275.3401	$275.34	$275.35	$275.30
Purchase #5	$48.47	9.173%	$52.9162	$52.92	$52.90	$52.90
Purchase #6	$214.55	7.760%	$231.1991	$231.20	$231.20	$231.20
Purchase #7	$165.40	4.200%	$172.3468	$172.35	$172.35	$172.30
7 purchase totals =	$1,096.16		$1,185.6470	$1,185.66	$1,185.60	$1,185.50