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	$58.67	3.115%	$60.4976	$60.50	$60.50	$60.50
Purchase #2	$124.55	10.203%	$137.2578	$137.26	$137.25	$137.30
Purchase #3	$166.92	9.835%	$183.3366	$183.34	$183.35	$183.30
Purchase #4	$15.31	11.128%	$17.0137	$17.01	$17.00	$17.00
Purchase #5	$6.98	12.594%	$7.8591	$7.86	$7.85	$7.90
Purchase #6	$160.42	5.413%	$169.1035	$169.10	$169.10	$169.10
Purchase #7	$89.53	3.282%	$92.4684	$92.47	$92.45	$92.50
7 purchase totals =	$622.38		$667.5367	$667.54	$667.50	$667.60