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	$181.72	4.257%	$189.4558	$189.46	$189.45	$189.50
Purchase #2	$87.51	3.543%	$90.6105	$90.61	$90.60	$90.60
Purchase #3	$173.46	11.597%	$193.5762	$193.58	$193.60	$193.60
Purchase #4	$129.44	4.190%	$134.8635	$134.86	$134.85	$134.90
Purchase #5	$88.78	13.193%	$100.4927	$100.49	$100.50	$100.50
Purchase #6	$234.39	10.315%	$258.5673	$258.57	$258.55	$258.60
Purchase #7	$71.36	11.117%	$79.2931	$79.29	$79.30	$79.30
7 purchase totals =	$966.66		$1,046.8591	$1,046.86	$1,046.85	$1,047.00