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	$48.89	7.621%	$52.6159	$52.62	$52.60	$52.60
Purchase #2	$193.74	5.818%	$205.0118	$205.01	$205.00	$205.00
Purchase #3	$120.40	13.329%	$136.4481	$136.45	$136.45	$136.40
Purchase #4	$11.40	8.690%	$12.3907	$12.39	$12.40	$12.40
Purchase #5	$164.96	3.124%	$170.1134	$170.11	$170.10	$170.10
Purchase #6	$44.45	11.730%	$49.664	$49.66	$49.65	$49.70
Purchase #7	$38.59	6.504%	$41.0999	$41.10	$41.10	$41.10
7 purchase totals =	$622.43		$667.3438	$667.34	$667.30	$667.30