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	$183.43	11.490%	$204.5061	$204.51	$204.50	$204.50
Purchase #2	$91.95	13.319%	$104.1968	$104.20	$104.20	$104.20
Purchase #3	$114.62	11.507%	$127.8093	$127.81	$127.80	$127.80
Purchase #4	$156.72	4.338%	$163.5185	$163.52	$163.50	$163.50
Purchase #5	$176.89	8.303%	$191.5772	$191.58	$191.60	$191.60
Purchase #6	$19.59	3.811%	$20.3366	$20.34	$20.35	$20.30
Purchase #7	$176.44	13.753%	$200.7058	$200.71	$200.70	$200.70
7 purchase totals =	$919.64		$1,012.6503	$1,012.67	$1,012.65	$1,012.60