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	$136.53	9.479%	$149.4717	$149.47	$149.45	$149.50
Purchase #2	$47.97	8.704%	$52.1453	$52.15	$52.15	$52.10
Purchase #3	$216.60	12.137%	$242.8887	$242.89	$242.90	$242.90
Purchase #4	$224.30	13.765%	$255.1749	$255.17	$255.15	$255.20
Purchase #5	$44.43	12.736%	$50.0886	$50.09	$50.10	$50.10
Purchase #6	$9.90	13.111%	$11.198	$11.20	$11.20	$11.20
Purchase #7	$53.42	4.660%	$55.9094	$55.91	$55.90	$55.90
7 purchase totals =	$733.15		$816.8766	$816.88	$816.85	$816.90