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	$245.65	7.140%	$263.1894	$263.19	$263.20	$263.20
Purchase #2	$52.89	11.625%	$59.0385	$59.04	$59.05	$59.00
Purchase #3	$165.74	4.340%	$172.9331	$172.93	$172.95	$172.90
Purchase #4	$140.77	9.620%	$154.3121	$154.31	$154.30	$154.30
Purchase #5	$122.79	4.206%	$127.9545	$127.95	$127.95	$128.00
Purchase #6	$160.60	3.438%	$166.1214	$166.12	$166.10	$166.10
Purchase #7	$163.43	9.812%	$179.4658	$179.47	$179.45	$179.50
7 purchase totals =	$1,051.87		$1,123.0148	$1,123.01	$1,123.00	$1,123.00