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	$37.75	13.453%	$42.8285	$42.83	$42.85	$42.80
Purchase #2	$225.79	3.667%	$234.0697	$234.07	$234.05	$234.10
Purchase #3	$105.42	9.229%	$115.1492	$115.15	$115.15	$115.10
Purchase #4	$196.72	11.122%	$218.5992	$218.60	$218.60	$218.60
Purchase #5	$197.44	12.503%	$222.1259	$222.13	$222.15	$222.10
Purchase #6	$54.87	10.195%	$60.464	$60.46	$60.45	$60.50
Purchase #7	$130.58	13.851%	$148.6666	$148.67	$148.65	$148.70
7 purchase totals =	$948.57		$1,041.9031	$1,041.91	$1,041.90	$1,041.90