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	$105.94	3.696%	$109.8555	$109.86	$109.85	$109.90
Purchase #2	$185.49	3.657%	$192.2734	$192.27	$192.25	$192.30
Purchase #3	$74.56	11.776%	$83.3402	$83.34	$83.35	$83.30
Purchase #4	$53.44	11.778%	$59.7342	$59.73	$59.75	$59.70
Purchase #5	$11.91	13.585%	$13.528	$13.53	$13.55	$13.50
Purchase #6	$240.32	7.394%	$258.0893	$258.09	$258.10	$258.10
Purchase #7	$135.91	7.394%	$145.9592	$145.96	$145.95	$146.00
7 purchase totals =	$807.57		$862.7798	$862.78	$862.80	$862.80