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	$134.86	9.401%	$147.5382	$147.54	$147.55	$147.50
Purchase #2	$200.27	4.171%	$208.6233	$208.62	$208.60	$208.60
Purchase #3	$218.90	4.197%	$228.0872	$228.09	$228.10	$228.10
Purchase #4	$172.43	8.475%	$187.0434	$187.04	$187.05	$187.00
Purchase #5	$76.73	7.178%	$82.2377	$82.24	$82.25	$82.20
Purchase #6	$57.69	8.241%	$62.4442	$62.44	$62.45	$62.40
Purchase #7	$220.50	8.257%	$238.7067	$238.71	$238.70	$238.70
7 purchase totals =	$1,081.38		$1,154.6807	$1,154.68	$1,154.70	$1,154.50