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	$133.35	13.662%	$151.5683	$151.57	$151.55	$151.60
Purchase #2	$40.46	6.174%	$42.958	$42.96	$42.95	$43.00
Purchase #3	$129.27	9.631%	$141.72	$141.72	$141.70	$141.70
Purchase #4	$133.30	6.538%	$142.0152	$142.02	$142.00	$142.00
Purchase #5	$213.93	8.379%	$231.8552	$231.86	$231.85	$231.90
Purchase #6	$84.43	7.139%	$90.4575	$90.46	$90.45	$90.50
Purchase #7	$22.51	10.789%	$24.9386	$24.94	$24.95	$24.90
7 purchase totals =	$757.25		$825.5128	$825.53	$825.45	$825.60