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	$151.86	3.365%	$156.9701	$156.97	$156.95	$157.00
Purchase #2	$235.70	7.547%	$253.4883	$253.49	$253.50	$253.50
Purchase #3	$142.98	8.562%	$155.2219	$155.22	$155.20	$155.20
Purchase #4	$158.46	6.170%	$168.237	$168.24	$168.25	$168.20
Purchase #5	$177.62	13.522%	$201.6378	$201.64	$201.65	$201.60
Purchase #6	$83.38	8.483%	$90.4531	$90.45	$90.45	$90.50
Purchase #7	$40.88	12.254%	$45.8894	$45.89	$45.90	$45.90
7 purchase totals =	$990.88		$1,071.8976	$1,071.90	$1,071.90	$1,071.90