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	$31.43	4.483%	$32.839	$32.84	$32.85	$32.80
Purchase #2	$202.39	3.453%	$209.3785	$209.38	$209.40	$209.40
Purchase #3	$18.52	11.730%	$20.6924	$20.69	$20.70	$20.70
Purchase #4	$223.49	5.605%	$236.0166	$236.02	$236.00	$236.00
Purchase #5	$62.69	6.810%	$66.9592	$66.96	$66.95	$67.00
Purchase #6	$124.91	9.590%	$136.8889	$136.89	$136.90	$136.90
Purchase #7	$180.85	8.381%	$196.007	$196.01	$196.00	$196.00
7 purchase totals =	$844.28		$898.7816	$898.79	$898.80	$898.80