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	$37.79	13.601%	$42.9298	$42.93	$42.95	$42.90
Purchase #2	$37.35	12.728%	$42.1039	$42.10	$42.10	$42.10
Purchase #3	$59.74	12.595%	$67.2643	$67.26	$67.25	$67.30
Purchase #4	$48.61	13.762%	$55.2997	$55.30	$55.30	$55.30
Purchase #5	$108.35	5.537%	$114.3493	$114.35	$114.35	$114.30
Purchase #6	$81.83	6.265%	$86.9566	$86.96	$86.95	$87.00
Purchase #7	$40.56	9.670%	$44.4822	$44.48	$44.50	$44.50
7 purchase totals =	$414.23		$453.3858	$453.38	$453.40	$453.40