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	$69.47	5.324%	$73.1686	$73.17	$73.15	$73.20
Purchase #2	$181.49	5.736%	$191.9003	$191.90	$191.90	$191.90
Purchase #3	$222.26	12.326%	$249.6558	$249.66	$249.65	$249.70
Purchase #4	$19.66	9.168%	$21.4624	$21.46	$21.45	$21.50
Purchase #5	$48.71	9.625%	$53.3983	$53.40	$53.40	$53.40
Purchase #6	$26.28	13.761%	$29.8964	$29.90	$29.90	$29.90
Purchase #7	$248.59	3.160%	$256.4454	$256.45	$256.45	$256.40
7 purchase totals =	$816.46		$875.9272	$875.94	$875.90	$876.00