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	$153.65	3.132%	$158.4623	$158.46	$158.45	$158.50
Purchase #2	$175.91	7.843%	$189.7066	$189.71	$189.70	$189.70
Purchase #3	$97.88	13.781%	$111.3688	$111.37	$111.35	$111.40
Purchase #4	$238.78	12.437%	$268.4771	$268.48	$268.50	$268.50
Purchase #5	$206.32	9.554%	$226.0318	$226.03	$226.05	$226.00
Purchase #6	$24.52	13.630%	$27.8621	$27.86	$27.85	$27.90
Purchase #7	$242.95	12.183%	$272.5486	$272.55	$272.55	$272.50
7 purchase totals =	$1,140.01		$1,254.4573	$1,254.46	$1,254.45	$1,254.50