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	$57.38	7.530%	$61.7007	$61.70	$61.70	$61.70
Purchase #2	$136.50	10.179%	$150.3943	$150.39	$150.40	$150.40
Purchase #3	$95.61	11.323%	$106.4359	$106.44	$106.45	$106.40
Purchase #4	$239.91	6.432%	$255.341	$255.34	$255.35	$255.30
Purchase #5	$108.52	3.375%	$112.1826	$112.18	$112.20	$112.20
Purchase #6	$83.77	13.534%	$95.1074	$95.11	$95.10	$95.10
Purchase #7	$25.33	13.814%	$28.8291	$28.83	$28.85	$28.80
7 purchase totals =	$747.02		$809.9910	$809.99	$810.05	$809.90