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	$134.92	3.359%	$139.452	$139.45	$139.45	$139.50
Purchase #2	$81.45	12.304%	$91.4716	$91.47	$91.45	$91.50
Purchase #3	$55.65	6.512%	$59.2739	$59.27	$59.25	$59.30
Purchase #4	$133.64	5.256%	$140.6641	$140.66	$140.65	$140.70
Purchase #5	$84.81	9.158%	$92.5769	$92.58	$92.60	$92.60
Purchase #6	$70.30	8.405%	$76.2087	$76.21	$76.20	$76.20
Purchase #7	$240.84	11.843%	$269.3627	$269.36	$269.35	$269.40
7 purchase totals =	$801.61		$869.0099	$869.00	$868.95	$869.20