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	$143.29	12.267%	$160.8674	$160.87	$160.85	$160.90
Purchase #2	$197.48	11.856%	$220.8932	$220.89	$220.90	$220.90
Purchase #3	$178.48	3.774%	$185.2158	$185.22	$185.20	$185.20
Purchase #4	$137.77	12.187%	$154.56	$154.56	$154.55	$154.60
Purchase #5	$204.89	8.635%	$222.5823	$222.58	$222.60	$222.60
Purchase #6	$20.63	3.543%	$21.3609	$21.36	$21.35	$21.40
Purchase #7	$18.81	11.209%	$20.9184	$20.92	$20.90	$20.90
7 purchase totals =	$901.35		$986.3980	$986.40	$986.35	$986.50