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	$81.39	4.792%	$85.2902	$85.29	$85.30	$85.30
Purchase #2	$158.38	6.531%	$168.7238	$168.72	$168.70	$168.70
Purchase #3	$35.33	10.745%	$39.1262	$39.13	$39.15	$39.10
Purchase #4	$193.74	12.766%	$218.4728	$218.47	$218.45	$218.50
Purchase #5	$152.88	5.651%	$161.5192	$161.52	$161.50	$161.50
Purchase #6	$209.77	11.401%	$233.6859	$233.69	$233.70	$233.70
Purchase #7	$71.70	6.505%	$76.3641	$76.36	$76.35	$76.40
7 purchase totals =	$903.19		$983.1822	$983.18	$983.15	$983.20