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	$35.47	8.561%	$38.5066	$38.51	$38.50	$38.50
Purchase #2	$145.46	5.606%	$153.6145	$153.61	$153.60	$153.60
Purchase #3	$29.33	6.575%	$31.2584	$31.26	$31.25	$31.30
Purchase #4	$154.72	11.302%	$172.2065	$172.21	$172.20	$172.20
Purchase #5	$39.47	9.807%	$43.3408	$43.34	$43.35	$43.30
Purchase #6	$178.91	7.465%	$192.2656	$192.27	$192.25	$192.30
Purchase #7	$243.77	12.258%	$273.6513	$273.65	$273.65	$273.70
7 purchase totals =	$827.13		$904.8437	$904.85	$904.80	$904.90