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	$247.60	4.406%	$258.5093	$258.51	$258.50	$258.50
Purchase #2	$106.64	6.797%	$113.8883	$113.89	$113.90	$113.90
Purchase #3	$62.37	12.140%	$69.9417	$69.94	$69.95	$69.90
Purchase #4	$128.58	5.735%	$135.9541	$135.95	$135.95	$136.00
Purchase #5	$128.72	12.151%	$144.3608	$144.36	$144.35	$144.40
Purchase #6	$148.81	11.145%	$165.3949	$165.39	$165.40	$165.40
Purchase #7	$140.67	12.394%	$158.1046	$158.10	$158.10	$158.10
7 purchase totals =	$963.39		$1,046.1537	$1,046.14	$1,046.15	$1,046.20