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	$182.78	6.241%	$194.1873	$194.19	$194.20	$194.20
Purchase #2	$43.53	7.765%	$46.9101	$46.91	$46.90	$46.90
Purchase #3	$99.91	8.445%	$108.3474	$108.35	$108.35	$108.30
Purchase #4	$99.43	12.574%	$111.9323	$111.93	$111.95	$111.90
Purchase #5	$64.37	7.536%	$69.2209	$69.22	$69.20	$69.20
Purchase #6	$159.70	7.720%	$172.0288	$172.03	$172.05	$172.00
Purchase #7	$29.91	13.156%	$33.845	$33.85	$33.85	$33.80
7 purchase totals =	$679.63		$736.4718	$736.48	$736.50	$736.30