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	$50.77	4.708%	$53.1603	$53.16	$53.15	$53.20
Purchase #2	$208.50	11.274%	$232.0063	$232.01	$232.00	$232.00
Purchase #3	$179.96	11.310%	$200.3135	$200.31	$200.30	$200.30
Purchase #4	$109.40	7.823%	$117.9584	$117.96	$117.95	$118.00
Purchase #5	$134.54	5.824%	$142.3756	$142.38	$142.40	$142.40
Purchase #6	$199.70	11.801%	$223.2666	$223.27	$223.25	$223.30
Purchase #7	$108.94	8.768%	$118.4919	$118.49	$118.50	$118.50
7 purchase totals =	$991.81		$1,087.5726	$1,087.58	$1,087.55	$1,087.70