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	$227.80	12.756%	$256.8582	$256.86	$256.85	$256.90
Purchase #2	$45.64	11.767%	$51.0105	$51.01	$51.00	$51.00
Purchase #3	$39.44	9.296%	$43.1063	$43.11	$43.10	$43.10
Purchase #4	$68.75	5.163%	$72.2996	$72.30	$72.30	$72.30
Purchase #5	$216.78	12.825%	$244.582	$244.58	$244.60	$244.60
Purchase #6	$196.33	8.295%	$212.6156	$212.62	$212.60	$212.60
Purchase #7	$216.80	3.371%	$224.1083	$224.11	$224.10	$224.10
7 purchase totals =	$1,011.54		$1,104.5805	$1,104.59	$1,104.55	$1,104.60