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	$235.59	3.429%	$243.6684	$243.67	$243.65	$243.70
Purchase #2	$222.28	8.830%	$241.9073	$241.91	$241.90	$241.90
Purchase #3	$120.66	9.262%	$131.8355	$131.84	$131.85	$131.80
Purchase #4	$92.41	3.409%	$95.5603	$95.56	$95.55	$95.60
Purchase #5	$237.62	5.429%	$250.5204	$250.52	$250.50	$250.50
Purchase #6	$214.96	10.518%	$237.5695	$237.57	$237.55	$237.60
Purchase #7	$52.53	5.814%	$55.5841	$55.58	$55.60	$55.60
7 purchase totals =	$1,176.05		$1,256.6455	$1,256.65	$1,256.60	$1,256.70