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	$220.59	10.325%	$243.3659	$243.37	$243.35	$243.40
Purchase #2	$157.96	10.285%	$174.2062	$174.21	$174.20	$174.20
Purchase #3	$38.38	4.414%	$40.0741	$40.07	$40.05	$40.10
Purchase #4	$212.54	4.767%	$222.6718	$222.67	$222.65	$222.70
Purchase #5	$208.25	7.873%	$224.6455	$224.65	$224.65	$224.60
Purchase #6	$85.77	11.400%	$95.5478	$95.55	$95.55	$95.50
Purchase #7	$145.89	4.330%	$152.207	$152.21	$152.20	$152.20
7 purchase totals =	$1,069.38		$1,152.7183	$1,152.73	$1,152.65	$1,152.70