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	$233.86	11.235%	$260.1342	$260.13	$260.15	$260.10
Purchase #2	$199.86	6.330%	$212.5111	$212.51	$212.50	$212.50
Purchase #3	$58.59	6.649%	$62.4856	$62.49	$62.50	$62.50
Purchase #4	$10.91	11.418%	$12.1557	$12.16	$12.15	$12.20
Purchase #5	$22.46	13.240%	$25.4337	$25.43	$25.45	$25.40
Purchase #6	$200.71	4.206%	$209.1519	$209.15	$209.15	$209.20
Purchase #7	$66.42	8.321%	$71.9468	$71.95	$71.95	$71.90
7 purchase totals =	$792.81		$853.8190	$853.82	$853.85	$853.80