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	$23.89	6.572%	$25.4601	$25.46	$25.45	$25.50
Purchase #2	$245.71	4.401%	$256.5237	$256.52	$256.50	$256.50
Purchase #3	$209.38	11.802%	$234.091	$234.09	$234.10	$234.10
Purchase #4	$227.34	6.220%	$241.4805	$241.48	$241.50	$241.50
Purchase #5	$217.90	11.201%	$242.307	$242.31	$242.30	$242.30
Purchase #6	$101.58	3.484%	$105.119	$105.12	$105.10	$105.10
Purchase #7	$234.34	9.732%	$257.146	$257.15	$257.15	$257.10
7 purchase totals =	$1,260.14		$1,362.1273	$1,362.13	$1,362.10	$1,362.10