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	$49.89	10.138%	$54.9478	$54.95	$54.95	$54.90
Purchase #2	$82.69	12.228%	$92.8013	$92.80	$92.80	$92.80
Purchase #3	$175.26	8.337%	$189.8714	$189.87	$189.85	$189.90
Purchase #4	$126.81	11.680%	$141.6214	$141.62	$141.60	$141.60
Purchase #5	$138.98	9.828%	$152.639	$152.64	$152.65	$152.60
Purchase #6	$239.93	5.755%	$253.738	$253.74	$253.75	$253.70
Purchase #7	$131.96	9.414%	$144.3827	$144.38	$144.40	$144.40
7 purchase totals =	$945.52		$1,030.0016	$1,030.00	$1,030.00	$1,029.90