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	$148.83	13.223%	$168.5098	$168.51	$168.50	$168.50
Purchase #2	$21.76	12.282%	$24.4326	$24.43	$24.45	$24.40
Purchase #3	$54.30	11.386%	$60.4826	$60.48	$60.50	$60.50
Purchase #4	$123.59	10.403%	$136.4471	$136.45	$136.45	$136.40
Purchase #5	$105.90	7.494%	$113.8361	$113.84	$113.85	$113.80
Purchase #6	$68.48	12.481%	$77.027	$77.03	$77.05	$77.00
Purchase #7	$132.81	7.127%	$142.2754	$142.28	$142.30	$142.30
7 purchase totals =	$655.67		$723.0106	$723.02	$723.10	$722.90