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	$210.53	4.136%	$219.2375	$219.24	$219.25	$219.20
Purchase #2	$73.71	4.136%	$76.7586	$76.76	$76.75	$76.80
Purchase #3	$20.52	8.786%	$22.3229	$22.32	$22.30	$22.30
Purchase #4	$63.61	11.648%	$71.0193	$71.02	$71.00	$71.00
Purchase #5	$72.49	13.245%	$82.0913	$82.09	$82.10	$82.10
Purchase #6	$84.81	9.106%	$92.5328	$92.53	$92.55	$92.50
Purchase #7	$129.31	13.301%	$146.5095	$146.51	$146.50	$146.50
7 purchase totals =	$654.98		$710.4719	$710.47	$710.45	$710.40