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	$245.35	4.670%	$256.8078	$256.81	$256.80	$256.80
Purchase #2	$63.93	13.539%	$72.5855	$72.59	$72.60	$72.60
Purchase #3	$132.51	13.643%	$150.5883	$150.59	$150.60	$150.60
Purchase #4	$37.80	11.400%	$42.1092	$42.11	$42.10	$42.10
Purchase #5	$19.36	7.112%	$20.7369	$20.74	$20.75	$20.70
Purchase #6	$132.36	5.811%	$140.0514	$140.05	$140.05	$140.10
Purchase #7	$121.43	9.318%	$132.7448	$132.74	$132.75	$132.70
7 purchase totals =	$752.74		$815.6239	$815.63	$815.65	$815.60