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	$20.75	5.249%	$21.8392	$21.84	$21.85	$21.80
Purchase #2	$7.80	13.589%	$8.8599	$8.86	$8.85	$8.90
Purchase #3	$105.83	4.867%	$110.9807	$110.98	$111.00	$111.00
Purchase #4	$86.70	6.824%	$92.6164	$92.62	$92.60	$92.60
Purchase #5	$44.96	8.737%	$48.8882	$48.89	$48.90	$48.90
Purchase #6	$186.78	11.846%	$208.906	$208.91	$208.90	$208.90
Purchase #7	$233.59	4.227%	$243.4638	$243.46	$243.45	$243.50
7 purchase totals =	$686.41		$735.5542	$735.56	$735.55	$735.60