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	$211.33	5.147%	$222.2072	$222.21	$222.20	$222.20
Purchase #2	$31.80	8.477%	$34.4957	$34.50	$34.50	$34.50
Purchase #3	$37.89	4.103%	$39.4446	$39.44	$39.45	$39.40
Purchase #4	$61.25	5.314%	$64.5048	$64.50	$64.50	$64.50
Purchase #5	$40.38	3.726%	$41.8846	$41.88	$41.90	$41.90
Purchase #6	$233.98	7.815%	$252.2655	$252.27	$252.25	$252.30
Purchase #7	$249.40	9.494%	$273.078	$273.08	$273.10	$273.10
7 purchase totals =	$866.03		$927.8804	$927.88	$927.90	$927.90