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	$120.58	13.845%	$137.2743	$137.27	$137.25	$137.30
Purchase #2	$171.70	11.184%	$190.9029	$190.90	$190.90	$190.90
Purchase #3	$45.96	3.103%	$47.3861	$47.39	$47.40	$47.40
Purchase #4	$137.37	12.811%	$154.9685	$154.97	$154.95	$155.00
Purchase #5	$184.86	7.619%	$198.9445	$198.94	$198.95	$198.90
Purchase #6	$109.97	5.850%	$116.4032	$116.40	$116.40	$116.40
Purchase #7	$88.50	9.488%	$96.8969	$96.90	$96.90	$96.90
7 purchase totals =	$858.94		$942.7764	$942.77	$942.75	$942.80