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	$144.28	6.676%	$153.9121	$153.91	$153.90	$153.90
Purchase #2	$224.35	13.143%	$253.8363	$253.84	$253.85	$253.80
Purchase #3	$139.88	8.581%	$151.8831	$151.88	$151.90	$151.90
Purchase #4	$207.76	4.741%	$217.6099	$217.61	$217.60	$217.60
Purchase #5	$175.96	4.254%	$183.4453	$183.45	$183.45	$183.40
Purchase #6	$151.88	3.244%	$156.807	$156.81	$156.80	$156.80
Purchase #7	$75.86	9.395%	$82.987	$82.99	$83.00	$83.00
7 purchase totals =	$1,119.97		$1,200.4807	$1,200.49	$1,200.50	$1,200.40