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	$127.85	3.138%	$131.8619	$131.86	$131.85	$131.90
Purchase #2	$149.44	3.557%	$154.7556	$154.76	$154.75	$154.80
Purchase #3	$131.62	9.725%	$144.42	$144.42	$144.40	$144.40
Purchase #4	$98.89	6.563%	$105.3802	$105.38	$105.40	$105.40
Purchase #5	$118.97	11.629%	$132.805	$132.81	$132.80	$132.80
Purchase #6	$203.57	3.603%	$210.9046	$210.90	$210.90	$210.90
Purchase #7	$115.59	8.707%	$125.6544	$125.65	$125.65	$125.70
7 purchase totals =	$945.93		$1,005.7817	$1,005.78	$1,005.75	$1,005.90