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	$190.81	7.341%	$204.8174	$204.82	$204.80	$204.80
Purchase #2	$104.41	11.539%	$116.4579	$116.46	$116.45	$116.50
Purchase #3	$14.78	4.742%	$15.4809	$15.48	$15.50	$15.50
Purchase #4	$110.61	7.179%	$118.5507	$118.55	$118.55	$118.60
Purchase #5	$127.92	12.506%	$143.9177	$143.92	$143.90	$143.90
Purchase #6	$174.86	3.666%	$181.2704	$181.27	$181.25	$181.30
Purchase #7	$102.95	11.853%	$115.1527	$115.15	$115.15	$115.20
7 purchase totals =	$826.34		$895.6477	$895.65	$895.60	$895.80