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	$74.34	7.812%	$80.1474	$80.15	$80.15	$80.10
Purchase #2	$112.89	10.418%	$124.6509	$124.65	$124.65	$124.70
Purchase #3	$141.59	6.195%	$150.3615	$150.36	$150.35	$150.40
Purchase #4	$192.46	8.528%	$208.873	$208.87	$208.85	$208.90
Purchase #5	$150.76	4.366%	$157.3422	$157.34	$157.35	$157.30
Purchase #6	$203.66	9.619%	$223.2501	$223.25	$223.25	$223.30
Purchase #7	$117.38	5.345%	$123.654	$123.65	$123.65	$123.70
7 purchase totals =	$993.08		$1,068.2791	$1,068.27	$1,068.25	$1,068.40