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	$89.85	4.248%	$93.6668	$93.67	$93.65	$93.70
Purchase #2	$147.67	11.188%	$164.1913	$164.19	$164.20	$164.20
Purchase #3	$62.63	3.111%	$64.5784	$64.58	$64.60	$64.60
Purchase #4	$246.95	11.139%	$274.4578	$274.46	$274.45	$274.50
Purchase #5	$247.99	9.637%	$271.8888	$271.89	$271.90	$271.90
Purchase #6	$43.37	9.557%	$47.5149	$47.51	$47.50	$47.50
Purchase #7	$82.48	9.778%	$90.5449	$90.54	$90.55	$90.50
7 purchase totals =	$920.94		$1,006.8429	$1,006.84	$1,006.85	$1,006.90