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	$224.57	4.268%	$234.1546	$234.15	$234.15	$234.20
Purchase #2	$192.70	12.442%	$216.6757	$216.68	$216.70	$216.70
Purchase #3	$20.50	6.865%	$21.9073	$21.91	$21.90	$21.90
Purchase #4	$170.83	11.520%	$190.5096	$190.51	$190.50	$190.50
Purchase #5	$208.35	4.240%	$217.184	$217.18	$217.20	$217.20
Purchase #6	$183.92	6.747%	$196.3291	$196.33	$196.35	$196.30
Purchase #7	$72.94	11.826%	$81.5659	$81.57	$81.55	$81.60
7 purchase totals =	$1,073.81		$1,158.3262	$1,158.33	$1,158.35	$1,158.40