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	$55.56	10.730%	$61.5216	$61.52	$61.50	$61.50
Purchase #2	$247.37	11.772%	$276.4904	$276.49	$276.50	$276.50
Purchase #3	$73.94	9.357%	$80.8586	$80.86	$80.85	$80.90
Purchase #4	$240.35	6.513%	$256.004	$256.00	$256.00	$256.00
Purchase #5	$165.27	11.854%	$184.8611	$184.86	$184.85	$184.90
Purchase #6	$122.34	13.652%	$139.0419	$139.04	$139.05	$139.00
Purchase #7	$46.52	8.111%	$50.2932	$50.29	$50.30	$50.30
7 purchase totals =	$951.35		$1,049.0708	$1,049.06	$1,049.05	$1,049.10