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	$59.42	13.389%	$67.3757	$67.38	$67.40	$67.40
Purchase #2	$204.54	10.290%	$225.5872	$225.59	$225.60	$225.60
Purchase #3	$193.43	7.667%	$208.2603	$208.26	$208.25	$208.30
Purchase #4	$178.76	9.641%	$195.9943	$195.99	$196.00	$196.00
Purchase #5	$167.70	4.823%	$175.7882	$175.79	$175.80	$175.80
Purchase #6	$61.64	9.245%	$67.3386	$67.34	$67.35	$67.30
Purchase #7	$101.84	11.296%	$113.3438	$113.34	$113.35	$113.30
7 purchase totals =	$967.33		$1,053.6881	$1,053.69	$1,053.75	$1,053.70