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	$202.25	11.568%	$225.6463	$225.65	$225.65	$225.60
Purchase #2	$100.77	5.778%	$106.5925	$106.59	$106.60	$106.60
Purchase #3	$121.51	4.822%	$127.3692	$127.37	$127.35	$127.40
Purchase #4	$192.81	8.326%	$208.8634	$208.86	$208.85	$208.90
Purchase #5	$243.46	5.192%	$256.1004	$256.10	$256.10	$256.10
Purchase #6	$222.88	7.489%	$239.5715	$239.57	$239.55	$239.60
Purchase #7	$56.34	4.535%	$58.895	$58.90	$58.90	$58.90
7 purchase totals =	$1,140.02		$1,223.0383	$1,223.04	$1,223.00	$1,223.10