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	$144.98	11.193%	$161.2076	$161.21	$161.20	$161.20
Purchase #2	$35.93	13.428%	$40.7547	$40.75	$40.75	$40.80
Purchase #3	$179.38	9.780%	$196.9234	$196.92	$196.90	$196.90
Purchase #4	$204.67	8.776%	$222.6318	$222.63	$222.65	$222.60
Purchase #5	$88.75	13.480%	$100.7135	$100.71	$100.70	$100.70
Purchase #6	$25.47	10.657%	$28.1843	$28.18	$28.20	$28.20
Purchase #7	$195.81	11.123%	$217.5899	$217.59	$217.60	$217.60
7 purchase totals =	$874.99		$968.0052	$967.99	$968.00	$968.00