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	$78.76	8.750%	$85.6515	$85.65	$85.65	$85.70
Purchase #2	$22.94	9.360%	$25.0872	$25.09	$25.10	$25.10
Purchase #3	$182.74	4.304%	$190.6051	$190.61	$190.60	$190.60
Purchase #4	$76.65	9.213%	$83.7118	$83.71	$83.70	$83.70
Purchase #5	$216.96	12.413%	$243.8912	$243.89	$243.90	$243.90
Purchase #6	$120.70	8.485%	$130.9414	$130.94	$130.95	$130.90
Purchase #7	$93.48	10.610%	$103.3982	$103.40	$103.40	$103.40
7 purchase totals =	$792.23		$863.2864	$863.29	$863.30	$863.30