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	$134.57	12.251%	$151.0562	$151.06	$151.05	$151.10
Purchase #2	$159.68	13.353%	$181.0021	$181.00	$181.00	$181.00
Purchase #3	$71.60	10.130%	$78.8531	$78.85	$78.85	$78.90
Purchase #4	$203.59	11.541%	$227.0863	$227.09	$227.10	$227.10
Purchase #5	$139.72	7.836%	$150.6685	$150.67	$150.65	$150.70
Purchase #6	$244.68	10.353%	$270.0117	$270.01	$270.00	$270.00
Purchase #7	$152.51	4.164%	$158.8605	$158.86	$158.85	$158.90
7 purchase totals =	$1,106.35		$1,217.5384	$1,217.54	$1,217.50	$1,217.70