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	$135.96	12.323%	$152.7144	$152.71	$152.70	$152.70
Purchase #2	$43.85	4.263%	$45.7193	$45.72	$45.70	$45.70
Purchase #3	$37.42	9.260%	$40.8851	$40.89	$40.90	$40.90
Purchase #4	$105.45	8.856%	$114.7887	$114.79	$114.80	$114.80
Purchase #5	$127.46	11.328%	$141.8987	$141.90	$141.90	$141.90
Purchase #6	$184.68	13.358%	$209.3496	$209.35	$209.35	$209.30
Purchase #7	$192.51	10.365%	$212.4637	$212.46	$212.45	$212.50
7 purchase totals =	$827.33		$917.8195	$917.82	$917.80	$917.80