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	$41.89	8.561%	$45.4762	$45.48	$45.50	$45.50
Purchase #2	$136.37	3.830%	$141.593	$141.59	$141.60	$141.60
Purchase #3	$207.50	5.511%	$218.9353	$218.94	$218.95	$218.90
Purchase #4	$231.84	5.630%	$244.8926	$244.89	$244.90	$244.90
Purchase #5	$250.65	3.195%	$258.6583	$258.66	$258.65	$258.70
Purchase #6	$67.28	13.621%	$76.4442	$76.44	$76.45	$76.40
Purchase #7	$99.51	7.346%	$106.82	$106.82	$106.80	$106.80
7 purchase totals =	$1,035.04		$1,092.8196	$1,092.82	$1,092.85	$1,092.80