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	$102.48	6.378%	$109.0162	$109.02	$109.00	$109.00
Purchase #2	$128.67	10.248%	$141.8561	$141.86	$141.85	$141.90
Purchase #3	$36.41	6.346%	$38.7206	$38.72	$38.70	$38.70
Purchase #4	$207.34	8.462%	$224.8851	$224.89	$224.90	$224.90
Purchase #5	$204.60	11.462%	$228.0513	$228.05	$228.05	$228.10
Purchase #6	$183.67	3.723%	$190.508	$190.51	$190.50	$190.50
Purchase #7	$117.43	7.565%	$126.3136	$126.31	$126.30	$126.30
7 purchase totals =	$980.60		$1,059.3509	$1,059.36	$1,059.30	$1,059.40