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	$87.61	5.481%	$92.4119	$92.41	$92.40	$92.40
Purchase #2	$38.45	4.384%	$40.1356	$40.14	$40.15	$40.10
Purchase #3	$50.40	9.206%	$55.0398	$55.04	$55.05	$55.00
Purchase #4	$75.26	8.751%	$81.846	$81.85	$81.85	$81.80
Purchase #5	$48.43	8.259%	$52.4298	$52.43	$52.45	$52.40
Purchase #6	$159.34	8.457%	$172.8154	$172.82	$172.80	$172.80
Purchase #7	$239.96	11.335%	$267.1595	$267.16	$267.15	$267.20
7 purchase totals =	$699.45		$761.8380	$761.85	$761.85	$761.70