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	$143.85	4.475%	$150.2873	$150.29	$150.30	$150.30
Purchase #2	$140.82	5.401%	$148.4257	$148.43	$148.45	$148.40
Purchase #3	$126.93	8.165%	$137.2938	$137.29	$137.30	$137.30
Purchase #4	$120.39	9.682%	$132.0462	$132.05	$132.05	$132.00
Purchase #5	$40.59	5.805%	$42.9462	$42.95	$42.95	$42.90
Purchase #6	$5.95	3.328%	$6.148	$6.15	$6.15	$6.10
Purchase #7	$119.99	8.391%	$130.0584	$130.06	$130.05	$130.10
7 purchase totals =	$698.52		$747.2056	$747.22	$747.25	$747.10