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	$63.38	12.754%	$71.4635	$71.46	$71.45	$71.50
Purchase #2	$42.48	13.155%	$48.0682	$48.07	$48.05	$48.10
Purchase #3	$19.55	6.250%	$20.7719	$20.77	$20.75	$20.80
Purchase #4	$17.63	6.652%	$18.8027	$18.80	$18.80	$18.80
Purchase #5	$44.34	3.285%	$45.7966	$45.80	$45.80	$45.80
Purchase #6	$32.48	3.825%	$33.7224	$33.72	$33.70	$33.70
Purchase #7	$236.54	5.345%	$249.1831	$249.18	$249.20	$249.20
7 purchase totals =	$456.40		$487.8084	$487.80	$487.75	$487.90