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	$208.96	6.463%	$222.4651	$222.47	$222.45	$222.50
Purchase #2	$230.80	7.510%	$248.1331	$248.13	$248.15	$248.10
Purchase #3	$14.57	3.218%	$15.0389	$15.04	$15.05	$15.00
Purchase #4	$32.99	8.684%	$35.8549	$35.85	$35.85	$35.90
Purchase #5	$205.54	4.536%	$214.8633	$214.86	$214.85	$214.90
Purchase #6	$244.61	11.534%	$272.8233	$272.82	$272.80	$272.80
Purchase #7	$154.85	6.640%	$165.132	$165.13	$165.15	$165.10
7 purchase totals =	$1,092.32		$1,174.3106	$1,174.30	$1,174.30	$1,174.30