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	$235.77	8.424%	$255.6313	$255.63	$255.65	$255.60
Purchase #2	$232.71	4.340%	$242.8096	$242.81	$242.80	$242.80
Purchase #3	$13.30	11.833%	$14.8738	$14.87	$14.85	$14.90
Purchase #4	$119.39	3.162%	$123.1651	$123.17	$123.15	$123.20
Purchase #5	$107.32	10.860%	$118.975	$118.98	$119.00	$119.00
Purchase #6	$64.57	10.165%	$71.1335	$71.13	$71.15	$71.10
Purchase #7	$33.39	5.388%	$35.1891	$35.19	$35.20	$35.20
7 purchase totals =	$806.45		$861.7774	$861.78	$861.80	$861.80