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	$82.95	6.770%	$88.5657	$88.57	$88.55	$88.60
Purchase #2	$143.78	5.578%	$151.8	$151.80	$151.80	$151.80
Purchase #3	$141.34	12.359%	$158.8082	$158.81	$158.80	$158.80
Purchase #4	$71.68	9.295%	$78.3427	$78.34	$78.35	$78.30
Purchase #5	$80.62	9.523%	$88.2974	$88.30	$88.30	$88.30
Purchase #6	$225.45	8.844%	$245.3888	$245.39	$245.40	$245.40
Purchase #7	$48.74	8.749%	$53.0043	$53.00	$53.00	$53.00
7 purchase totals =	$794.56		$864.2071	$864.21	$864.20	$864.20