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	$87.45	4.754%	$91.6074	$91.61	$91.60	$91.60
Purchase #2	$141.70	8.413%	$153.6212	$153.62	$153.60	$153.60
Purchase #3	$119.28	3.478%	$123.4286	$123.43	$123.45	$123.40
Purchase #4	$203.95	12.703%	$229.8578	$229.86	$229.85	$229.90
Purchase #5	$134.69	9.179%	$147.0532	$147.05	$147.05	$147.10
Purchase #6	$50.25	8.675%	$54.6092	$54.61	$54.60	$54.60
Purchase #7	$195.35	6.785%	$208.6045	$208.60	$208.60	$208.60
7 purchase totals =	$932.67		$1,008.7819	$1,008.78	$1,008.75	$1,008.80