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	$248.37	13.490%	$281.8751	$281.88	$281.90	$281.90
Purchase #2	$165.31	11.500%	$184.3207	$184.32	$184.30	$184.30
Purchase #3	$62.29	7.433%	$66.92	$66.92	$66.90	$66.90
Purchase #4	$26.62	13.830%	$30.3015	$30.30	$30.30	$30.30
Purchase #5	$220.46	5.178%	$231.8754	$231.88	$231.90	$231.90
Purchase #6	$53.49	4.795%	$56.0548	$56.05	$56.05	$56.10
Purchase #7	$48.36	10.676%	$53.5229	$53.52	$53.50	$53.50
7 purchase totals =	$824.90		$904.8704	$904.87	$904.85	$904.90