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	$199.63	4.778%	$209.1683	$209.17	$209.15	$209.20
Purchase #2	$196.70	9.821%	$216.0179	$216.02	$216.00	$216.00
Purchase #3	$148.45	13.153%	$167.9756	$167.98	$168.00	$168.00
Purchase #4	$86.37	7.230%	$92.6146	$92.61	$92.60	$92.60
Purchase #5	$93.81	12.601%	$105.631	$105.63	$105.65	$105.60
Purchase #6	$241.32	8.224%	$261.1662	$261.17	$261.15	$261.20
Purchase #7	$157.82	8.530%	$171.282	$171.28	$171.30	$171.30
7 purchase totals =	$1,124.10		$1,223.8556	$1,223.86	$1,223.85	$1,223.90