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	$194.89	11.128%	$216.5774	$216.58	$216.60	$216.60
Purchase #2	$140.99	5.336%	$148.5132	$148.51	$148.50	$148.50
Purchase #3	$172.74	13.635%	$196.2931	$196.29	$196.30	$196.30
Purchase #4	$161.55	7.498%	$173.663	$173.66	$173.65	$173.70
Purchase #5	$106.89	11.869%	$119.5768	$119.58	$119.60	$119.60
Purchase #6	$197.62	7.311%	$212.068	$212.07	$212.05	$212.10
Purchase #7	$40.48	12.724%	$45.6307	$45.63	$45.65	$45.60
7 purchase totals =	$1,015.16		$1,112.3222	$1,112.32	$1,112.35	$1,112.40