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	$30.36	6.339%	$32.2845	$32.28	$32.30	$32.30
Purchase #2	$205.57	12.799%	$231.8809	$231.88	$231.90	$231.90
Purchase #3	$175.52	11.813%	$196.2542	$196.25	$196.25	$196.30
Purchase #4	$125.45	12.567%	$141.2153	$141.22	$141.20	$141.20
Purchase #5	$201.58	11.395%	$224.55	$224.55	$224.55	$224.60
Purchase #6	$89.70	8.823%	$97.6142	$97.61	$97.60	$97.60
Purchase #7	$214.86	13.835%	$244.5859	$244.59	$244.60	$244.60
7 purchase totals =	$1,043.04		$1,168.3850	$1,168.38	$1,168.40	$1,168.50