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	$236.75	7.711%	$255.0058	$255.01	$255.00	$255.00
Purchase #2	$63.74	5.573%	$67.2922	$67.29	$67.30	$67.30
Purchase #3	$216.98	13.406%	$246.0683	$246.07	$246.05	$246.10
Purchase #4	$81.28	5.447%	$85.7073	$85.71	$85.70	$85.70
Purchase #5	$93.27	7.310%	$100.088	$100.09	$100.10	$100.10
Purchase #6	$137.69	7.533%	$148.0622	$148.06	$148.05	$148.10
Purchase #7	$195.37	11.835%	$218.492	$218.49	$218.50	$218.50
7 purchase totals =	$1,025.08		$1,120.7158	$1,120.72	$1,120.70	$1,120.80