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	$31.40	6.281%	$33.3722	$33.37	$33.35	$33.40
Purchase #2	$129.37	9.806%	$142.056	$142.06	$142.05	$142.10
Purchase #3	$6.25	12.770%	$7.0481	$7.05	$7.05	$7.00
Purchase #4	$56.94	10.531%	$62.9364	$62.94	$62.95	$62.90
Purchase #5	$45.26	11.700%	$50.5554	$50.56	$50.55	$50.60
Purchase #6	$247.25	8.822%	$269.0624	$269.06	$269.05	$269.10
Purchase #7	$56.88	8.130%	$61.5043	$61.50	$61.50	$61.50
7 purchase totals =	$573.35		$626.5348	$626.54	$626.50	$626.60