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	$220.52	10.635%	$243.9723	$243.97	$243.95	$244.00
Purchase #2	$103.89	8.709%	$112.9378	$112.94	$112.95	$112.90
Purchase #3	$149.41	5.803%	$158.0803	$158.08	$158.10	$158.10
Purchase #4	$240.41	6.718%	$256.5607	$256.56	$256.55	$256.60
Purchase #5	$231.48	11.438%	$257.9567	$257.96	$257.95	$258.00
Purchase #6	$116.85	12.113%	$131.004	$131.00	$131.00	$131.00
Purchase #7	$177.59	4.324%	$185.269	$185.27	$185.25	$185.30
7 purchase totals =	$1,240.15		$1,345.7808	$1,345.78	$1,345.75	$1,345.90