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	$122.59	7.658%	$131.9779	$131.98	$132.00	$132.00
Purchase #2	$151.25	3.603%	$156.6995	$156.70	$156.70	$156.70
Purchase #3	$143.97	8.513%	$156.2262	$156.23	$156.25	$156.20
Purchase #4	$11.83	10.601%	$13.0841	$13.08	$13.10	$13.10
Purchase #5	$84.54	5.759%	$89.4087	$89.41	$89.40	$89.40
Purchase #6	$139.90	7.843%	$150.8724	$150.87	$150.85	$150.90
Purchase #7	$48.68	13.398%	$55.2021	$55.20	$55.20	$55.20
7 purchase totals =	$702.76		$753.4709	$753.47	$753.50	$753.50