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	$247.89	7.214%	$265.7728	$265.77	$265.75	$265.80
Purchase #2	$160.63	6.460%	$171.0067	$171.01	$171.00	$171.00
Purchase #3	$33.75	13.696%	$38.3724	$38.37	$38.35	$38.40
Purchase #4	$225.43	9.106%	$245.9577	$245.96	$245.95	$246.00
Purchase #5	$221.46	13.852%	$252.1366	$252.14	$252.15	$252.10
Purchase #6	$59.86	13.162%	$67.7388	$67.74	$67.75	$67.70
Purchase #7	$94.29	5.536%	$99.5099	$99.51	$99.50	$99.50
7 purchase totals =	$1,043.31		$1,140.4949	$1,140.50	$1,140.45	$1,140.50