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	$103.32	7.379%	$110.944	$110.94	$110.95	$110.90
Purchase #2	$152.47	9.105%	$166.3524	$166.35	$166.35	$166.40
Purchase #3	$47.78	9.267%	$52.2078	$52.21	$52.20	$52.20
Purchase #4	$37.53	13.505%	$42.5984	$42.60	$42.60	$42.60
Purchase #5	$153.47	13.760%	$174.5875	$174.59	$174.60	$174.60
Purchase #6	$188.98	8.438%	$204.9261	$204.93	$204.95	$204.90
Purchase #7	$169.33	12.136%	$189.8799	$189.88	$189.90	$189.90
7 purchase totals =	$852.88		$941.4961	$941.50	$941.55	$941.50