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	$250.86	11.138%	$278.8008	$278.80	$278.80	$278.80
Purchase #2	$21.27	7.530%	$22.8716	$22.87	$22.85	$22.90
Purchase #3	$67.33	7.870%	$72.6289	$72.63	$72.65	$72.60
Purchase #4	$172.77	5.427%	$182.1462	$182.15	$182.15	$182.10
Purchase #5	$108.94	3.784%	$113.0623	$113.06	$113.05	$113.10
Purchase #6	$36.86	5.814%	$39.003	$39.00	$39.00	$39.00
Purchase #7	$11.54	12.325%	$12.9623	$12.96	$12.95	$13.00
7 purchase totals =	$669.57		$721.4751	$721.47	$721.45	$721.50