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	$234.89	3.738%	$243.6702	$243.67	$243.65	$243.70
Purchase #2	$86.68	6.282%	$92.1252	$92.13	$92.15	$92.10
Purchase #3	$214.25	7.298%	$229.886	$229.89	$229.90	$229.90
Purchase #4	$80.25	11.759%	$89.6866	$89.69	$89.70	$89.70
Purchase #5	$72.81	9.342%	$79.6119	$79.61	$79.60	$79.60
Purchase #6	$10.61	6.210%	$11.2689	$11.27	$11.25	$11.30
Purchase #7	$233.29	10.521%	$257.8344	$257.83	$257.85	$257.80
7 purchase totals =	$932.78		$1,004.0832	$1,004.09	$1,004.10	$1,004.10