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	$65.26	10.205%	$71.9198	$71.92	$71.90	$71.90
Purchase #2	$195.54	13.791%	$222.5069	$222.51	$222.50	$222.50
Purchase #3	$132.87	6.534%	$141.5517	$141.55	$141.55	$141.60
Purchase #4	$204.92	5.121%	$215.414	$215.41	$215.40	$215.40
Purchase #5	$232.54	9.565%	$254.7825	$254.78	$254.80	$254.80
Purchase #6	$112.52	8.791%	$122.4116	$122.41	$122.40	$122.40
Purchase #7	$78.86	11.373%	$87.8287	$87.83	$87.85	$87.80
7 purchase totals =	$1,022.51		$1,116.4152	$1,116.41	$1,116.40	$1,116.40