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	$198.70	8.131%	$214.8563	$214.86	$214.85	$214.90
Purchase #2	$9.78	5.326%	$10.3009	$10.30	$10.30	$10.30
Purchase #3	$216.58	13.351%	$245.4956	$245.50	$245.50	$245.50
Purchase #4	$127.72	6.862%	$136.4841	$136.48	$136.50	$136.50
Purchase #5	$203.96	13.503%	$231.5007	$231.50	$231.50	$231.50
Purchase #6	$201.90	10.449%	$222.9965	$223.00	$223.00	$223.00
Purchase #7	$244.60	13.867%	$278.5187	$278.52	$278.50	$278.50
7 purchase totals =	$1,203.24		$1,340.1528	$1,340.16	$1,340.15	$1,340.20