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	$234.29	9.284%	$256.0415	$256.04	$256.05	$256.00
Purchase #2	$119.38	6.311%	$126.9141	$126.91	$126.90	$126.90
Purchase #3	$208.55	10.256%	$229.9389	$229.94	$229.95	$229.90
Purchase #4	$88.64	11.684%	$98.9967	$99.00	$99.00	$99.00
Purchase #5	$152.31	8.155%	$164.7309	$164.73	$164.75	$164.70
Purchase #6	$137.97	11.683%	$154.089	$154.09	$154.10	$154.10
Purchase #7	$82.46	8.228%	$89.2448	$89.24	$89.25	$89.20
7 purchase totals =	$1,023.60		$1,119.9559	$1,119.95	$1,120.00	$1,119.80