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	$87.75	8.382%	$95.1052	$95.11	$95.10	$95.10
Purchase #2	$124.79	13.439%	$141.5605	$141.56	$141.55	$141.60
Purchase #3	$181.40	8.322%	$196.4961	$196.50	$196.50	$196.50
Purchase #4	$101.59	3.521%	$105.167	$105.17	$105.15	$105.20
Purchase #5	$160.96	12.519%	$181.1106	$181.11	$181.10	$181.10
Purchase #6	$115.61	3.146%	$119.2471	$119.25	$119.25	$119.20
Purchase #7	$133.79	4.640%	$139.9979	$140.00	$140.00	$140.00
7 purchase totals =	$905.89		$978.6844	$978.70	$978.65	$978.70