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	$151.86	13.268%	$172.0088	$172.01	$172.00	$172.00
Purchase #2	$231.90	10.518%	$256.2912	$256.29	$256.30	$256.30
Purchase #3	$33.28	13.730%	$37.8493	$37.85	$37.85	$37.80
Purchase #4	$74.38	9.270%	$81.275	$81.28	$81.30	$81.30
Purchase #5	$108.98	9.295%	$119.1097	$119.11	$119.10	$119.10
Purchase #6	$96.80	8.856%	$105.3726	$105.37	$105.35	$105.40
Purchase #7	$168.63	8.446%	$182.8725	$182.87	$182.85	$182.90
7 purchase totals =	$865.83		$954.7791	$954.78	$954.75	$954.80