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	$219.33	13.464%	$248.8606	$248.86	$248.85	$248.90
Purchase #2	$236.45	3.105%	$243.7918	$243.79	$243.80	$243.80
Purchase #3	$216.66	13.617%	$246.1626	$246.16	$246.15	$246.20
Purchase #4	$47.86	9.758%	$52.5302	$52.53	$52.55	$52.50
Purchase #5	$35.34	13.129%	$39.9798	$39.98	$40.00	$40.00
Purchase #6	$82.76	9.505%	$90.6263	$90.63	$90.65	$90.60
Purchase #7	$226.54	10.278%	$249.8238	$249.82	$249.80	$249.80
7 purchase totals =	$1,064.94		$1,171.7751	$1,171.77	$1,171.80	$1,171.80