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	$100.38	13.161%	$113.591	$113.59	$113.60	$113.60
Purchase #2	$238.91	12.459%	$268.6758	$268.68	$268.70	$268.70
Purchase #3	$30.38	5.204%	$31.961	$31.96	$31.95	$32.00
Purchase #4	$208.68	6.434%	$222.1065	$222.11	$222.10	$222.10
Purchase #5	$79.49	13.300%	$90.0622	$90.06	$90.05	$90.10
Purchase #6	$171.44	5.706%	$181.2224	$181.22	$181.20	$181.20
Purchase #7	$113.84	3.183%	$117.4635	$117.46	$117.45	$117.50
7 purchase totals =	$943.12		$1,025.0824	$1,025.08	$1,025.05	$1,025.20