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	$234.33	6.505%	$249.5732	$249.57	$249.55	$249.60
Purchase #2	$11.83	9.455%	$12.9485	$12.95	$12.95	$12.90
Purchase #3	$120.40	9.846%	$132.2546	$132.25	$132.25	$132.30
Purchase #4	$110.53	8.795%	$120.2511	$120.25	$120.25	$120.30
Purchase #5	$136.86	10.293%	$150.947	$150.95	$150.95	$150.90
Purchase #6	$106.75	4.729%	$111.7982	$111.80	$111.80	$111.80
Purchase #7	$223.32	4.826%	$234.0974	$234.10	$234.10	$234.10
7 purchase totals =	$944.02		$1,011.8700	$1,011.87	$1,011.85	$1,011.90