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	$64.51	8.716%	$70.1327	$70.13	$70.15	$70.10
Purchase #2	$117.61	11.592%	$131.2434	$131.24	$131.25	$131.20
Purchase #3	$231.52	13.471%	$262.7081	$262.71	$262.70	$262.70
Purchase #4	$243.32	8.413%	$263.7905	$263.79	$263.80	$263.80
Purchase #5	$18.30	10.768%	$20.2705	$20.27	$20.25	$20.30
Purchase #6	$53.55	3.684%	$55.5228	$55.52	$55.50	$55.50
Purchase #7	$236.94	5.256%	$249.3936	$249.39	$249.40	$249.40
7 purchase totals =	$965.75		$1,053.0616	$1,053.05	$1,053.05	$1,053.00