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	$64.31	12.579%	$72.3996	$72.40	$72.40	$72.40
Purchase #2	$171.88	13.271%	$194.6902	$194.69	$194.70	$194.70
Purchase #3	$222.94	5.162%	$234.4482	$234.45	$234.45	$234.40
Purchase #4	$78.62	3.705%	$81.5329	$81.53	$81.55	$81.50
Purchase #5	$164.30	8.271%	$177.8893	$177.89	$177.90	$177.90
Purchase #6	$89.35	6.833%	$95.4553	$95.46	$95.45	$95.50
Purchase #7	$90.82	6.412%	$96.6434	$96.64	$96.65	$96.60
7 purchase totals =	$882.22		$953.0589	$953.06	$953.10	$953.00