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	$151.42	4.672%	$158.4943	$158.49	$158.50	$158.50
Purchase #2	$153.63	11.452%	$171.2237	$171.22	$171.20	$171.20
Purchase #3	$222.78	11.624%	$248.6759	$248.68	$248.70	$248.70
Purchase #4	$59.66	13.426%	$67.67	$67.67	$67.65	$67.70
Purchase #5	$226.34	12.485%	$254.5985	$254.60	$254.60	$254.60
Purchase #6	$136.91	6.565%	$145.8981	$145.90	$145.90	$145.90
Purchase #7	$61.56	4.324%	$64.2219	$64.22	$64.20	$64.20
7 purchase totals =	$1,012.30		$1,110.7824	$1,110.78	$1,110.75	$1,110.80