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	$37.69	11.132%	$41.8857	$41.89	$41.90	$41.90
Purchase #2	$153.65	12.597%	$173.0053	$173.01	$173.00	$173.00
Purchase #3	$48.83	12.412%	$54.8908	$54.89	$54.90	$54.90
Purchase #4	$34.81	6.597%	$37.1064	$37.11	$37.10	$37.10
Purchase #5	$113.73	10.800%	$126.0128	$126.01	$126.00	$126.00
Purchase #6	$87.39	12.739%	$98.5226	$98.52	$98.50	$98.50
Purchase #7	$140.81	4.435%	$147.0549	$147.05	$147.05	$147.10
7 purchase totals =	$616.91		$678.4785	$678.48	$678.45	$678.50