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	$154.66	8.850%	$168.3474	$168.35	$168.35	$168.30
Purchase #2	$141.79	12.110%	$158.9608	$158.96	$158.95	$159.00
Purchase #3	$156.68	9.593%	$171.7103	$171.71	$171.70	$171.70
Purchase #4	$105.67	11.161%	$117.4638	$117.46	$117.45	$117.50
Purchase #5	$139.67	4.689%	$146.2191	$146.22	$146.20	$146.20
Purchase #6	$127.32	10.307%	$140.4429	$140.44	$140.45	$140.40
Purchase #7	$116.35	13.343%	$131.8746	$131.87	$131.85	$131.90
7 purchase totals =	$942.14		$1,035.0189	$1,035.01	$1,034.95	$1,035.00