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	$39.89	4.425%	$41.6551	$41.66	$41.65	$41.70
Purchase #2	$246.76	7.233%	$264.6082	$264.61	$264.60	$264.60
Purchase #3	$220.68	9.650%	$241.9756	$241.98	$242.00	$242.00
Purchase #4	$30.68	3.460%	$31.7415	$31.74	$31.75	$31.70
Purchase #5	$219.25	12.872%	$247.4719	$247.47	$247.45	$247.50
Purchase #6	$78.57	10.451%	$86.7814	$86.78	$86.80	$86.80
Purchase #7	$132.89	10.776%	$147.2102	$147.21	$147.20	$147.20
7 purchase totals =	$968.72		$1,061.4439	$1,061.45	$1,061.45	$1,061.50