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	$54.97	7.723%	$59.2153	$59.22	$59.20	$59.20
Purchase #2	$32.56	7.439%	$34.9821	$34.98	$35.00	$35.00
Purchase #3	$169.99	12.143%	$190.6319	$190.63	$190.65	$190.60
Purchase #4	$172.55	8.131%	$186.58	$186.58	$186.60	$186.60
Purchase #5	$63.30	12.362%	$71.1251	$71.13	$71.15	$71.10
Purchase #6	$216.55	9.761%	$237.6874	$237.69	$237.70	$237.70
Purchase #7	$205.32	13.746%	$233.5433	$233.54	$233.55	$233.50
7 purchase totals =	$915.24		$1,013.7651	$1,013.77	$1,013.85	$1,013.70