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	$67.94	10.437%	$75.0309	$75.03	$75.05	$75.00
Purchase #2	$49.72	11.331%	$55.3538	$55.35	$55.35	$55.40
Purchase #3	$211.81	13.801%	$241.0419	$241.04	$241.05	$241.00
Purchase #4	$91.30	9.609%	$100.073	$100.07	$100.05	$100.10
Purchase #5	$33.68	13.503%	$38.2278	$38.23	$38.25	$38.20
Purchase #6	$48.72	4.453%	$50.8895	$50.89	$50.90	$50.90
Purchase #7	$156.27	9.810%	$171.6001	$171.60	$171.60	$171.60
7 purchase totals =	$659.44		$732.2170	$732.21	$732.25	$732.20