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	$64.68	13.442%	$73.3743	$73.37	$73.35	$73.40
Purchase #2	$162.67	12.181%	$182.4848	$182.48	$182.50	$182.50
Purchase #3	$20.52	9.767%	$22.5242	$22.52	$22.50	$22.50
Purchase #4	$72.76	4.573%	$76.0873	$76.09	$76.10	$76.10
Purchase #5	$132.94	11.338%	$148.0127	$148.01	$148.00	$148.00
Purchase #6	$250.42	5.560%	$264.3434	$264.34	$264.35	$264.30
Purchase #7	$51.95	13.822%	$59.1305	$59.13	$59.15	$59.10
7 purchase totals =	$755.94		$825.9572	$825.94	$825.95	$825.90