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	$13.39	9.418%	$14.6511	$14.65	$14.65	$14.70
Purchase #2	$163.39	5.514%	$172.3993	$172.40	$172.40	$172.40
Purchase #3	$232.70	4.823%	$243.9231	$243.92	$243.90	$243.90
Purchase #4	$243.52	13.253%	$275.7937	$275.79	$275.80	$275.80
Purchase #5	$65.77	10.405%	$72.6134	$72.61	$72.60	$72.60
Purchase #6	$145.73	13.381%	$165.2301	$165.23	$165.25	$165.20
Purchase #7	$24.55	10.198%	$27.0536	$27.05	$27.05	$27.10
7 purchase totals =	$889.05		$971.6643	$971.65	$971.65	$971.70