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	$105.76	6.659%	$112.8026	$112.80	$112.80	$112.80
Purchase #2	$200.54	10.427%	$221.4503	$221.45	$221.45	$221.50
Purchase #3	$60.50	8.637%	$65.7254	$65.73	$65.75	$65.70
Purchase #4	$174.66	4.718%	$182.9005	$182.90	$182.90	$182.90
Purchase #5	$110.51	13.584%	$125.5217	$125.52	$125.50	$125.50
Purchase #6	$169.86	12.823%	$191.6411	$191.64	$191.65	$191.60
Purchase #7	$211.88	12.576%	$238.526	$238.53	$238.55	$238.50
7 purchase totals =	$1,033.71		$1,138.5676	$1,138.57	$1,138.60	$1,138.50