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	$97.49	7.218%	$104.5268	$104.53	$104.55	$104.50
Purchase #2	$122.58	8.524%	$133.0287	$133.03	$133.05	$133.00
Purchase #3	$208.57	10.835%	$231.1686	$231.17	$231.15	$231.20
Purchase #4	$149.31	11.396%	$166.3254	$166.33	$166.35	$166.30
Purchase #5	$53.72	10.735%	$59.4868	$59.49	$59.50	$59.50
Purchase #6	$121.36	12.256%	$136.2339	$136.23	$136.25	$136.20
Purchase #7	$225.70	5.741%	$238.6574	$238.66	$238.65	$238.70
7 purchase totals =	$978.73		$1,069.4276	$1,069.44	$1,069.50	$1,069.40