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	$201.34	10.854%	$223.1934	$223.19	$223.20	$223.20
Purchase #2	$138.37	11.536%	$154.3324	$154.33	$154.35	$154.30
Purchase #3	$124.28	12.570%	$139.902	$139.90	$139.90	$139.90
Purchase #4	$178.47	7.548%	$191.9409	$191.94	$191.95	$191.90
Purchase #5	$165.83	6.813%	$177.128	$177.13	$177.15	$177.10
Purchase #6	$87.29	7.139%	$93.5216	$93.52	$93.50	$93.50
Purchase #7	$34.39	9.177%	$37.546	$37.55	$37.55	$37.50
7 purchase totals =	$929.97		$1,017.5643	$1,017.56	$1,017.60	$1,017.40