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	$131.92	13.774%	$150.0907	$150.09	$150.10	$150.10
Purchase #2	$188.46	6.293%	$200.3198	$200.32	$200.30	$200.30
Purchase #3	$44.30	6.107%	$47.0054	$47.01	$47.00	$47.00
Purchase #4	$72.25	13.521%	$82.0189	$82.02	$82.00	$82.00
Purchase #5	$37.48	3.795%	$38.9024	$38.90	$38.90	$38.90
Purchase #6	$132.25	12.607%	$148.9228	$148.92	$148.90	$148.90
Purchase #7	$25.75	5.210%	$27.0916	$27.09	$27.10	$27.10
7 purchase totals =	$632.41		$694.3516	$694.35	$694.30	$694.30