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	$39.63	8.123%	$42.8491	$42.85	$42.85	$42.80
Purchase #2	$225.29	10.288%	$248.4678	$248.47	$248.45	$248.50
Purchase #3	$180.52	8.851%	$196.4978	$196.50	$196.50	$196.50
Purchase #4	$158.74	13.114%	$179.5572	$179.56	$179.55	$179.60
Purchase #5	$172.42	3.625%	$178.6702	$178.67	$178.65	$178.70
Purchase #6	$135.64	12.603%	$152.7347	$152.73	$152.75	$152.70
Purchase #7	$210.44	3.283%	$217.3487	$217.35	$217.35	$217.30
7 purchase totals =	$1,122.68		$1,216.1255	$1,216.13	$1,216.10	$1,216.10