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	$140.75	4.148%	$146.5883	$146.59	$146.60	$146.60
Purchase #2	$66.78	7.777%	$71.9735	$71.97	$71.95	$72.00
Purchase #3	$58.81	3.840%	$61.0683	$61.07	$61.05	$61.10
Purchase #4	$105.75	12.431%	$118.8958	$118.90	$118.90	$118.90
Purchase #5	$132.94	13.391%	$150.742	$150.74	$150.75	$150.70
Purchase #6	$248.59	4.828%	$260.5919	$260.59	$260.60	$260.60
Purchase #7	$212.75	13.325%	$241.0989	$241.10	$241.10	$241.10
7 purchase totals =	$966.37		$1,050.9587	$1,050.96	$1,050.95	$1,051.00