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	$159.65	6.304%	$169.7143	$169.71	$169.70	$169.70
Purchase #2	$41.29	11.385%	$45.9909	$45.99	$46.00	$46.00
Purchase #3	$151.51	13.109%	$171.3714	$171.37	$171.35	$171.40
Purchase #4	$199.28	11.818%	$222.8309	$222.83	$222.85	$222.80
Purchase #5	$216.95	11.284%	$241.4306	$241.43	$241.45	$241.40
Purchase #6	$138.72	5.825%	$146.8004	$146.80	$146.80	$146.80
Purchase #7	$165.96	4.695%	$173.7518	$173.75	$173.75	$173.80
7 purchase totals =	$1,073.36		$1,171.8903	$1,171.88	$1,171.90	$1,171.90