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	$95.35	5.420%	$100.518	$100.52	$100.50	$100.50
Purchase #2	$97.66	6.248%	$103.7618	$103.76	$103.75	$103.80
Purchase #3	$196.93	10.164%	$216.946	$216.95	$216.95	$216.90
Purchase #4	$129.48	10.693%	$143.3253	$143.33	$143.35	$143.30
Purchase #5	$59.29	4.871%	$62.178	$62.18	$62.20	$62.20
Purchase #6	$223.75	8.221%	$242.1445	$242.14	$242.15	$242.10
Purchase #7	$213.27	3.477%	$220.6854	$220.69	$220.70	$220.70
7 purchase totals =	$1,015.73		$1,089.5590	$1,089.57	$1,089.60	$1,089.50