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	$180.30	7.641%	$194.0767	$194.08	$194.10	$194.10
Purchase #2	$69.93	12.146%	$78.4237	$78.42	$78.40	$78.40
Purchase #3	$100.70	5.863%	$106.604	$106.60	$106.60	$106.60
Purchase #4	$26.72	6.141%	$28.3609	$28.36	$28.35	$28.40
Purchase #5	$75.94	3.153%	$78.3344	$78.33	$78.35	$78.30
Purchase #6	$35.52	11.625%	$39.6492	$39.65	$39.65	$39.60
Purchase #7	$130.30	12.723%	$146.8781	$146.88	$146.90	$146.90
7 purchase totals =	$619.41		$672.3270	$672.32	$672.35	$672.30