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	$116.29	6.525%	$123.8779	$123.88	$123.90	$123.90
Purchase #2	$135.65	6.789%	$144.8593	$144.86	$144.85	$144.90
Purchase #3	$48.77	6.809%	$52.0907	$52.09	$52.10	$52.10
Purchase #4	$200.32	5.647%	$211.6321	$211.63	$211.65	$211.60
Purchase #5	$72.26	4.539%	$75.5399	$75.54	$75.55	$75.50
Purchase #6	$246.75	10.464%	$272.5699	$272.57	$272.55	$272.60
Purchase #7	$127.55	3.591%	$132.1303	$132.13	$132.15	$132.10
7 purchase totals =	$947.59		$1,012.7001	$1,012.70	$1,012.75	$1,012.70