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	$42.52	4.734%	$44.5329	$44.53	$44.55	$44.50
Purchase #2	$213.56	8.392%	$231.482	$231.48	$231.50	$231.50
Purchase #3	$221.83	10.253%	$244.5742	$244.57	$244.55	$244.60
Purchase #4	$231.64	12.798%	$261.2853	$261.29	$261.30	$261.30
Purchase #5	$145.53	13.700%	$165.4676	$165.47	$165.45	$165.50
Purchase #6	$244.33	12.263%	$274.2922	$274.29	$274.30	$274.30
Purchase #7	$131.31	10.306%	$144.8428	$144.84	$144.85	$144.80
7 purchase totals =	$1,230.72		$1,366.4770	$1,366.47	$1,366.50	$1,366.50