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	$132.40	12.269%	$148.6442	$148.64	$148.65	$148.60
Purchase #2	$50.81	8.176%	$54.9642	$54.96	$54.95	$55.00
Purchase #3	$144.58	4.427%	$150.9806	$150.98	$151.00	$151.00
Purchase #4	$228.60	6.706%	$243.9299	$243.93	$243.95	$243.90
Purchase #5	$137.98	10.131%	$151.9588	$151.96	$151.95	$152.00
Purchase #6	$155.78	4.175%	$162.2838	$162.28	$162.30	$162.30
Purchase #7	$204.28	9.520%	$223.7275	$223.73	$223.75	$223.70
7 purchase totals =	$1,054.43		$1,136.4890	$1,136.48	$1,136.55	$1,136.50