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	$43.40	3.608%	$44.9659	$44.97	$44.95	$45.00
Purchase #2	$238.58	7.162%	$255.6671	$255.67	$255.65	$255.70
Purchase #3	$145.29	6.558%	$154.8181	$154.82	$154.80	$154.80
Purchase #4	$208.56	11.395%	$232.3254	$232.33	$232.35	$232.30
Purchase #5	$149.41	10.698%	$165.3939	$165.39	$165.40	$165.40
Purchase #6	$9.69	7.624%	$10.4288	$10.43	$10.45	$10.40
Purchase #7	$209.62	3.471%	$216.8959	$216.90	$216.90	$216.90
7 purchase totals =	$1,004.55		$1,080.4951	$1,080.51	$1,080.50	$1,080.50