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	$169.61	10.730%	$187.8092	$187.81	$187.80	$187.80
Purchase #2	$249.33	11.360%	$277.6539	$277.65	$277.65	$277.70
Purchase #3	$103.39	10.759%	$114.5137	$114.51	$114.50	$114.50
Purchase #4	$60.31	7.715%	$64.9629	$64.96	$64.95	$65.00
Purchase #5	$143.27	9.484%	$156.8577	$156.86	$156.85	$156.90
Purchase #6	$40.85	10.105%	$44.9779	$44.98	$45.00	$45.00
Purchase #7	$154.84	4.797%	$162.2677	$162.27	$162.25	$162.30
7 purchase totals =	$921.60		$1,009.0430	$1,009.04	$1,009.00	$1,009.20