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	$178.80	9.707%	$196.1561	$196.16	$196.15	$196.20
Purchase #2	$38.48	11.477%	$42.8963	$42.90	$42.90	$42.90
Purchase #3	$129.38	9.634%	$141.8445	$141.84	$141.85	$141.80
Purchase #4	$198.29	5.191%	$208.5832	$208.58	$208.60	$208.60
Purchase #5	$94.77	3.359%	$97.9533	$97.95	$97.95	$98.00
Purchase #6	$192.33	11.581%	$214.6037	$214.60	$214.60	$214.60
Purchase #7	$197.95	5.616%	$209.0669	$209.07	$209.05	$209.10
7 purchase totals =	$1,030.00		$1,111.1040	$1,111.10	$1,111.10	$1,111.20