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	$150.90	12.349%	$169.5346	$169.53	$169.55	$169.50
Purchase #2	$163.40	5.599%	$172.5488	$172.55	$172.55	$172.50
Purchase #3	$207.97	6.787%	$222.0849	$222.08	$222.10	$222.10
Purchase #4	$109.89	10.360%	$121.2746	$121.27	$121.25	$121.30
Purchase #5	$40.71	6.299%	$43.2743	$43.27	$43.25	$43.30
Purchase #6	$208.42	10.748%	$230.821	$230.82	$230.80	$230.80
Purchase #7	$59.67	11.806%	$66.7146	$66.71	$66.70	$66.70
7 purchase totals =	$940.96		$1,026.2528	$1,026.23	$1,026.20	$1,026.20