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	$43.39	4.418%	$45.307	$45.31	$45.30	$45.30
Purchase #2	$197.48	10.839%	$218.8849	$218.88	$218.90	$218.90
Purchase #3	$124.93	6.374%	$132.893	$132.89	$132.90	$132.90
Purchase #4	$214.87	13.457%	$243.7851	$243.79	$243.80	$243.80
Purchase #5	$169.59	12.290%	$190.4326	$190.43	$190.45	$190.40
Purchase #6	$53.40	4.182%	$55.6332	$55.63	$55.65	$55.60
Purchase #7	$166.48	10.607%	$184.1385	$184.14	$184.15	$184.10
7 purchase totals =	$970.14		$1,071.0743	$1,071.07	$1,071.15	$1,071.00