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	$133.72	12.459%	$150.3802	$150.38	$150.40	$150.40
Purchase #2	$209.34	13.611%	$237.8333	$237.83	$237.85	$237.80
Purchase #3	$134.87	12.865%	$152.221	$152.22	$152.20	$152.20
Purchase #4	$175.72	12.772%	$198.163	$198.16	$198.15	$198.20
Purchase #5	$134.72	10.409%	$148.743	$148.74	$148.75	$148.70
Purchase #6	$141.45	5.172%	$148.7658	$148.77	$148.75	$148.80
Purchase #7	$5.81	11.847%	$6.4983	$6.50	$6.50	$6.50
7 purchase totals =	$935.63		$1,042.6046	$1,042.60	$1,042.60	$1,042.60