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	$55.87	6.373%	$59.4306	$59.43	$59.45	$59.40
Purchase #2	$209.81	10.859%	$232.5933	$232.59	$232.60	$232.60
Purchase #3	$192.54	8.807%	$209.497	$209.50	$209.50	$209.50
Purchase #4	$111.58	6.803%	$119.1708	$119.17	$119.15	$119.20
Purchase #5	$193.61	13.219%	$219.2033	$219.20	$219.20	$219.20
Purchase #6	$232.73	6.405%	$247.6364	$247.64	$247.65	$247.60
Purchase #7	$20.69	13.419%	$23.4664	$23.47	$23.45	$23.50
7 purchase totals =	$1,016.83		$1,110.9978	$1,111.00	$1,111.00	$1,111.00