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	$231.71	9.409%	$253.5116	$253.51	$253.50	$253.50
Purchase #2	$228.96	13.218%	$259.2239	$259.22	$259.20	$259.20
Purchase #3	$44.96	9.542%	$49.2501	$49.25	$49.25	$49.30
Purchase #4	$207.73	6.797%	$221.8494	$221.85	$221.85	$221.80
Purchase #5	$88.67	6.813%	$94.7111	$94.71	$94.70	$94.70
Purchase #6	$89.94	11.851%	$100.5988	$100.60	$100.60	$100.60
Purchase #7	$50.36	8.143%	$54.4608	$54.46	$54.45	$54.50
7 purchase totals =	$942.33		$1,033.6057	$1,033.60	$1,033.55	$1,033.60