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	$69.50	4.302%	$72.4899	$72.49	$72.50	$72.50
Purchase #2	$179.48	13.435%	$203.5931	$203.59	$203.60	$203.60
Purchase #3	$67.32	8.154%	$72.8093	$72.81	$72.80	$72.80
Purchase #4	$68.84	5.443%	$72.587	$72.59	$72.60	$72.60
Purchase #5	$174.65	9.768%	$191.7098	$191.71	$191.70	$191.70
Purchase #6	$29.47	8.624%	$32.0115	$32.01	$32.00	$32.00
Purchase #7	$113.84	5.534%	$120.1399	$120.14	$120.15	$120.10
7 purchase totals =	$703.10		$765.3405	$765.34	$765.35	$765.30