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	$13.94	12.672%	$15.7065	$15.71	$15.70	$15.70
Purchase #2	$209.54	4.191%	$218.3218	$218.32	$218.30	$218.30
Purchase #3	$84.46	6.866%	$90.259	$90.26	$90.25	$90.30
Purchase #4	$165.56	5.106%	$174.0135	$174.01	$174.00	$174.00
Purchase #5	$146.39	8.743%	$159.1889	$159.19	$159.20	$159.20
Purchase #6	$152.58	9.853%	$167.6137	$167.61	$167.60	$167.60
Purchase #7	$227.70	6.752%	$243.0743	$243.07	$243.05	$243.10
7 purchase totals =	$1,000.17		$1,068.1777	$1,068.17	$1,068.10	$1,068.20