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	$29.66	10.237%	$32.6963	$32.70	$32.70	$32.70
Purchase #2	$247.70	6.540%	$263.8996	$263.90	$263.90	$263.90
Purchase #3	$225.91	8.224%	$244.4888	$244.49	$244.50	$244.50
Purchase #4	$53.72	7.619%	$57.8129	$57.81	$57.80	$57.80
Purchase #5	$11.30	12.729%	$12.7384	$12.74	$12.75	$12.70
Purchase #6	$150.46	9.325%	$164.4904	$164.49	$164.50	$164.50
Purchase #7	$250.68	9.454%	$274.3793	$274.38	$274.40	$274.40
7 purchase totals =	$969.43		$1,050.5057	$1,050.51	$1,050.55	$1,050.50