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	$83.61	13.499%	$94.8965	$94.90	$94.90	$94.90
Purchase #2	$9.54	11.348%	$10.6226	$10.62	$10.60	$10.60
Purchase #3	$154.72	13.217%	$175.1693	$175.17	$175.15	$175.20
Purchase #4	$118.50	11.230%	$131.8076	$131.81	$131.80	$131.80
Purchase #5	$53.87	13.819%	$61.3143	$61.31	$61.30	$61.30
Purchase #6	$200.39	10.629%	$221.6895	$221.69	$221.70	$221.70
Purchase #7	$136.89	12.775%	$154.3777	$154.38	$154.40	$154.40
7 purchase totals =	$757.52		$849.8775	$849.88	$849.85	$849.90