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	$40.33	6.862%	$43.0974	$43.10	$43.10	$43.10
Purchase #2	$10.94	7.496%	$11.7601	$11.76	$11.75	$11.80
Purchase #3	$116.95	5.102%	$122.9168	$122.92	$122.90	$122.90
Purchase #4	$111.80	7.810%	$120.5316	$120.53	$120.55	$120.50
Purchase #5	$97.86	3.122%	$100.9152	$100.92	$100.90	$100.90
Purchase #6	$55.26	11.652%	$61.6989	$61.70	$61.70	$61.70
Purchase #7	$30.62	9.354%	$33.4842	$33.48	$33.50	$33.50
7 purchase totals =	$463.76		$494.4042	$494.41	$494.40	$494.40