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	$232.71	11.795%	$260.1581	$260.16	$260.15	$260.20
Purchase #2	$45.38	11.634%	$50.6595	$50.66	$50.65	$50.70
Purchase #3	$137.48	12.370%	$154.4863	$154.49	$154.50	$154.50
Purchase #4	$107.67	10.397%	$118.8644	$118.86	$118.85	$118.90
Purchase #5	$32.86	12.327%	$36.9107	$36.91	$36.90	$36.90
Purchase #6	$84.63	7.162%	$90.6912	$90.69	$90.70	$90.70
Purchase #7	$35.31	11.123%	$39.2375	$39.24	$39.25	$39.20
7 purchase totals =	$676.04		$751.0077	$751.01	$751.00	$751.10