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	$93.93	12.450%	$105.6243	$105.62	$105.60	$105.60
Purchase #2	$90.86	5.835%	$96.1617	$96.16	$96.15	$96.20
Purchase #3	$160.78	7.285%	$172.4928	$172.49	$172.50	$172.50
Purchase #4	$125.28	4.513%	$130.9339	$130.93	$130.95	$130.90
Purchase #5	$182.50	9.601%	$200.0218	$200.02	$200.00	$200.00
Purchase #6	$197.78	12.554%	$222.6093	$222.61	$222.60	$222.60
Purchase #7	$243.54	11.802%	$272.2826	$272.28	$272.30	$272.30
7 purchase totals =	$1,094.67		$1,200.1264	$1,200.11	$1,200.10	$1,200.10