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	$132.98	13.738%	$151.2488	$151.25	$151.25	$151.20
Purchase #2	$208.66	9.319%	$228.105	$228.11	$228.10	$228.10
Purchase #3	$28.74	9.825%	$31.5637	$31.56	$31.55	$31.60
Purchase #4	$58.52	4.593%	$61.2078	$61.21	$61.20	$61.20
Purchase #5	$81.52	10.511%	$90.0886	$90.09	$90.10	$90.10
Purchase #6	$160.66	6.563%	$171.2041	$171.20	$171.20	$171.20
Purchase #7	$143.89	5.353%	$151.5924	$151.59	$151.60	$151.60
7 purchase totals =	$814.97		$885.0104	$885.01	$885.00	$885.00