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	$217.51	10.544%	$240.4443	$240.44	$240.45	$240.40
Purchase #2	$216.72	12.464%	$243.732	$243.73	$243.75	$243.70
Purchase #3	$116.29	13.347%	$131.8112	$131.81	$131.80	$131.80
Purchase #4	$81.58	10.429%	$90.088	$90.09	$90.10	$90.10
Purchase #5	$47.88	3.114%	$49.371	$49.37	$49.35	$49.40
Purchase #6	$203.63	8.768%	$221.4843	$221.48	$221.50	$221.50
Purchase #7	$124.92	5.643%	$131.9692	$131.97	$131.95	$132.00
7 purchase totals =	$1,008.53		$1,108.9000	$1,108.89	$1,108.90	$1,108.90