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	$98.48	13.272%	$111.5503	$111.55	$111.55	$111.60
Purchase #2	$222.76	10.665%	$246.5174	$246.52	$246.50	$246.50
Purchase #3	$31.88	8.636%	$34.6332	$34.63	$34.65	$34.60
Purchase #4	$135.93	6.328%	$144.5317	$144.53	$144.55	$144.50
Purchase #5	$231.74	9.178%	$253.0091	$253.01	$253.00	$253.00
Purchase #6	$38.49	11.428%	$42.8886	$42.89	$42.90	$42.90
Purchase #7	$223.69	9.622%	$245.2135	$245.21	$245.20	$245.20
7 purchase totals =	$982.97		$1,078.3438	$1,078.34	$1,078.35	$1,078.30