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	$227.57	12.266%	$255.4837	$255.48	$255.50	$255.50
Purchase #2	$185.51	5.469%	$195.6555	$195.66	$195.65	$195.70
Purchase #3	$206.52	7.255%	$221.503	$221.50	$221.50	$221.50
Purchase #4	$93.52	7.867%	$100.8772	$100.88	$100.90	$100.90
Purchase #5	$220.36	3.752%	$228.6279	$228.63	$228.65	$228.60
Purchase #6	$45.79	8.575%	$49.7165	$49.72	$49.70	$49.70
Purchase #7	$38.85	12.556%	$43.728	$43.73	$43.75	$43.70
7 purchase totals =	$1,018.12		$1,095.5918	$1,095.60	$1,095.65	$1,095.60