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	$49.40	5.265%	$52.0009	$52.00	$52.00	$52.00
Purchase #2	$249.50	6.452%	$265.5977	$265.60	$265.60	$265.60
Purchase #3	$211.89	5.282%	$223.082	$223.08	$223.10	$223.10
Purchase #4	$10.73	10.873%	$11.8967	$11.90	$11.90	$11.90
Purchase #5	$65.95	10.171%	$72.6578	$72.66	$72.65	$72.70
Purchase #6	$43.69	11.835%	$48.8607	$48.86	$48.85	$48.90
Purchase #7	$221.97	4.381%	$231.6945	$231.69	$231.70	$231.70
7 purchase totals =	$853.13		$905.7903	$905.79	$905.80	$905.90