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	$72.46	3.679%	$75.1258	$75.13	$75.15	$75.10
Purchase #2	$158.71	13.825%	$180.6517	$180.65	$180.65	$180.70
Purchase #3	$17.88	4.414%	$18.6692	$18.67	$18.65	$18.70
Purchase #4	$84.29	9.775%	$92.5293	$92.53	$92.55	$92.50
Purchase #5	$166.43	10.802%	$184.4078	$184.41	$184.40	$184.40
Purchase #6	$54.25	10.331%	$59.8546	$59.85	$59.85	$59.90
Purchase #7	$127.72	10.567%	$141.2162	$141.22	$141.20	$141.20
7 purchase totals =	$681.74		$752.4546	$752.46	$752.45	$752.50