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	$118.62	6.698%	$126.5652	$126.57	$126.55	$126.60
Purchase #2	$52.94	8.488%	$57.4335	$57.43	$57.45	$57.40
Purchase #3	$55.54	10.755%	$61.5133	$61.51	$61.50	$61.50
Purchase #4	$238.69	8.454%	$258.8689	$258.87	$258.85	$258.90
Purchase #5	$248.86	6.684%	$265.4938	$265.49	$265.50	$265.50
Purchase #6	$151.81	11.432%	$169.1649	$169.16	$169.15	$169.20
Purchase #7	$186.58	13.658%	$212.0631	$212.06	$212.05	$212.10
7 purchase totals =	$1,053.04		$1,151.1027	$1,151.09	$1,151.05	$1,151.20