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	$88.67	13.631%	$100.7566	$100.76	$100.75	$100.80
Purchase #2	$126.85	10.726%	$140.4559	$140.46	$140.45	$140.50
Purchase #3	$169.30	4.812%	$177.4467	$177.45	$177.45	$177.40
Purchase #4	$41.32	11.131%	$45.9193	$45.92	$45.90	$45.90
Purchase #5	$82.93	9.300%	$90.6425	$90.64	$90.65	$90.60
Purchase #6	$67.33	3.532%	$69.7081	$69.71	$69.70	$69.70
Purchase #7	$112.73	6.137%	$119.6482	$119.65	$119.65	$119.60
7 purchase totals =	$689.13		$744.5773	$744.59	$744.55	$744.50