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	$63.25	3.128%	$65.2285	$65.23	$65.25	$65.20
Purchase #2	$72.52	13.596%	$82.3798	$82.38	$82.40	$82.40
Purchase #3	$84.77	4.464%	$88.5541	$88.55	$88.55	$88.60
Purchase #4	$130.78	6.398%	$139.1473	$139.15	$139.15	$139.10
Purchase #5	$230.53	7.380%	$247.5431	$247.54	$247.55	$247.50
Purchase #6	$212.99	11.729%	$237.9716	$237.97	$237.95	$238.00
Purchase #7	$233.31	6.555%	$248.6035	$248.60	$248.60	$248.60
7 purchase totals =	$1,028.15		$1,109.4279	$1,109.42	$1,109.45	$1,109.40