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	$89.79	4.606%	$93.9257	$93.93	$93.95	$93.90
Purchase #2	$209.85	6.168%	$222.7935	$222.79	$222.80	$222.80
Purchase #3	$198.92	11.734%	$222.2613	$222.26	$222.25	$222.30
Purchase #4	$122.47	5.616%	$129.3479	$129.35	$129.35	$129.30
Purchase #5	$29.53	13.800%	$33.6051	$33.61	$33.60	$33.60
Purchase #6	$185.79	13.176%	$210.2697	$210.27	$210.25	$210.30
Purchase #7	$188.53	5.638%	$199.1593	$199.16	$199.15	$199.20
7 purchase totals =	$1,024.88		$1,111.3625	$1,111.37	$1,111.35	$1,111.40