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	$95.38	3.232%	$98.4627	$98.46	$98.45	$98.50
Purchase #2	$116.84	9.428%	$127.8557	$127.86	$127.85	$127.90
Purchase #3	$32.82	12.433%	$36.9005	$36.90	$36.90	$36.90
Purchase #4	$72.26	13.632%	$82.1105	$82.11	$82.10	$82.10
Purchase #5	$140.58	13.689%	$159.824	$159.82	$159.80	$159.80
Purchase #6	$20.85	3.843%	$21.6513	$21.65	$21.65	$21.70
Purchase #7	$127.78	3.787%	$132.619	$132.62	$132.60	$132.60
7 purchase totals =	$606.51		$659.4237	$659.42	$659.35	$659.50