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	$100.42	9.484%	$109.9438	$109.94	$109.95	$109.90
Purchase #2	$173.79	9.838%	$190.8875	$190.89	$190.90	$190.90
Purchase #3	$240.78	11.783%	$269.1511	$269.15	$269.15	$269.20
Purchase #4	$166.25	4.666%	$174.0072	$174.01	$174.00	$174.00
Purchase #5	$240.84	13.233%	$272.7104	$272.71	$272.70	$272.70
Purchase #6	$17.57	13.874%	$20.0077	$20.01	$20.00	$20.00
Purchase #7	$116.71	4.198%	$121.6095	$121.61	$121.60	$121.60
7 purchase totals =	$1,056.36		$1,158.3172	$1,158.32	$1,158.30	$1,158.30