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	$55.40	10.374%	$61.1472	$61.15	$61.15	$61.10
Purchase #2	$192.48	6.412%	$204.8218	$204.82	$204.80	$204.80
Purchase #3	$123.54	3.164%	$127.4488	$127.45	$127.45	$127.40
Purchase #4	$108.96	3.183%	$112.4282	$112.43	$112.45	$112.40
Purchase #5	$164.97	4.491%	$172.3788	$172.38	$172.40	$172.40
Purchase #6	$112.59	11.668%	$125.727	$125.73	$125.75	$125.70
Purchase #7	$248.70	11.281%	$276.7558	$276.76	$276.75	$276.80
7 purchase totals =	$1,006.64		$1,080.7076	$1,080.72	$1,080.75	$1,080.60