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	$113.34	3.156%	$116.917	$116.92	$116.90	$116.90
Purchase #2	$59.90	9.627%	$65.6666	$65.67	$65.65	$65.70
Purchase #3	$8.79	11.854%	$9.832	$9.83	$9.85	$9.80
Purchase #4	$147.37	11.528%	$164.3588	$164.36	$164.35	$164.40
Purchase #5	$46.45	11.388%	$51.7397	$51.74	$51.75	$51.70
Purchase #6	$75.35	9.466%	$82.4826	$82.48	$82.50	$82.50
Purchase #7	$28.31	4.297%	$29.5265	$29.53	$29.55	$29.50
7 purchase totals =	$479.51		$520.5232	$520.53	$520.55	$520.50