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	$161.66	11.571%	$180.3657	$180.37	$180.35	$180.40
Purchase #2	$32.32	3.518%	$33.457	$33.46	$33.45	$33.50
Purchase #3	$75.34	11.294%	$83.8489	$83.85	$83.85	$83.80
Purchase #4	$233.81	8.179%	$252.9333	$252.93	$252.95	$252.90
Purchase #5	$133.57	11.301%	$148.6647	$148.66	$148.65	$148.70
Purchase #6	$102.74	8.777%	$111.7575	$111.76	$111.75	$111.80
Purchase #7	$175.39	11.865%	$196.2	$196.20	$196.20	$196.20
7 purchase totals =	$914.83		$1,007.2271	$1,007.23	$1,007.20	$1,007.30