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	$118.31	13.339%	$134.0914	$134.09	$134.10	$134.10
Purchase #2	$84.72	6.262%	$90.0252	$90.03	$90.05	$90.00
Purchase #3	$48.61	8.465%	$52.7248	$52.72	$52.70	$52.70
Purchase #4	$119.90	11.439%	$133.6154	$133.62	$133.60	$133.60
Purchase #5	$157.45	5.234%	$165.6909	$165.69	$165.70	$165.70
Purchase #6	$137.50	8.500%	$149.1875	$149.19	$149.20	$149.20
Purchase #7	$37.78	11.728%	$42.2108	$42.21	$42.20	$42.20
7 purchase totals =	$704.27		$767.5460	$767.55	$767.55	$767.50