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	$152.69	3.582%	$158.1594	$158.16	$158.15	$158.20
Purchase #2	$219.53	4.105%	$228.5417	$228.54	$228.55	$228.50
Purchase #3	$160.87	5.597%	$169.8739	$169.87	$169.85	$169.90
Purchase #4	$81.80	8.529%	$88.7767	$88.78	$88.80	$88.80
Purchase #5	$199.49	11.704%	$222.8383	$222.84	$222.85	$222.80
Purchase #6	$227.66	3.352%	$235.2912	$235.29	$235.30	$235.30
Purchase #7	$43.43	11.279%	$48.3285	$48.33	$48.35	$48.30
7 purchase totals =	$1,085.47		$1,151.8097	$1,151.81	$1,151.85	$1,151.80