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	$153.67	4.457%	$160.5191	$160.52	$160.50	$160.50
Purchase #2	$67.55	6.846%	$72.1745	$72.17	$72.15	$72.20
Purchase #3	$14.75	6.509%	$15.7101	$15.71	$15.70	$15.70
Purchase #4	$92.66	3.513%	$95.9151	$95.92	$95.90	$95.90
Purchase #5	$157.84	8.734%	$171.6257	$171.63	$171.65	$171.60
Purchase #6	$85.47	5.755%	$90.3888	$90.39	$90.40	$90.40
Purchase #7	$132.25	11.209%	$147.0739	$147.07	$147.05	$147.10
7 purchase totals =	$704.19		$753.4072	$753.41	$753.35	$753.40