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	$141.59	12.325%	$159.041	$159.04	$159.05	$159.00
Purchase #2	$222.49	8.199%	$240.732	$240.73	$240.75	$240.70
Purchase #3	$172.82	12.106%	$193.7416	$193.74	$193.75	$193.70
Purchase #4	$151.80	5.772%	$160.5619	$160.56	$160.55	$160.60
Purchase #5	$73.34	12.468%	$82.484	$82.48	$82.50	$82.50
Purchase #6	$146.89	3.180%	$151.5611	$151.56	$151.55	$151.60
Purchase #7	$208.68	4.193%	$217.43	$217.43	$217.45	$217.40
7 purchase totals =	$1,117.61		$1,205.5516	$1,205.54	$1,205.60	$1,205.50