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	$20.30	12.573%	$22.8523	$22.85	$22.85	$22.90
Purchase #2	$246.25	4.345%	$256.9496	$256.95	$256.95	$256.90
Purchase #3	$73.80	6.678%	$78.7284	$78.73	$78.75	$78.70
Purchase #4	$19.78	8.278%	$21.4174	$21.42	$21.40	$21.40
Purchase #5	$210.34	6.479%	$223.9679	$223.97	$223.95	$224.00
Purchase #6	$88.52	13.433%	$100.4109	$100.41	$100.40	$100.40
Purchase #7	$213.30	5.750%	$225.5648	$225.56	$225.55	$225.60
7 purchase totals =	$872.29		$929.8913	$929.89	$929.85	$929.90