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	$195.81	7.125%	$209.7615	$209.76	$209.75	$209.80
Purchase #2	$145.70	4.226%	$151.8573	$151.86	$151.85	$151.90
Purchase #3	$148.26	5.411%	$156.2823	$156.28	$156.30	$156.30
Purchase #4	$80.61	11.760%	$90.0897	$90.09	$90.10	$90.10
Purchase #5	$116.58	6.693%	$124.3827	$124.38	$124.40	$124.40
Purchase #6	$32.99	13.722%	$37.5169	$37.52	$37.50	$37.50
Purchase #7	$202.48	8.788%	$220.2739	$220.27	$220.25	$220.30
7 purchase totals =	$922.43		$990.1643	$990.16	$990.15	$990.30