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	$6.92	3.373%	$7.1534	$7.15	$7.15	$7.20
Purchase #2	$201.90	6.750%	$215.5283	$215.53	$215.55	$215.50
Purchase #3	$48.56	10.202%	$53.5141	$53.51	$53.50	$53.50
Purchase #4	$85.44	6.208%	$90.7441	$90.74	$90.75	$90.70
Purchase #5	$139.67	5.497%	$147.3477	$147.35	$147.35	$147.30
Purchase #6	$184.81	3.621%	$191.502	$191.50	$191.50	$191.50
Purchase #7	$136.46	13.283%	$154.586	$154.59	$154.60	$154.60
7 purchase totals =	$803.76		$860.3756	$860.37	$860.40	$860.30