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	$216.89	8.610%	$235.5642	$235.56	$235.55	$235.60
Purchase #2	$150.99	11.212%	$167.919	$167.92	$167.90	$167.90
Purchase #3	$169.65	4.193%	$176.7634	$176.76	$176.75	$176.80
Purchase #4	$171.44	7.800%	$184.8123	$184.81	$184.80	$184.80
Purchase #5	$115.81	4.236%	$120.7157	$120.72	$120.70	$120.70
Purchase #6	$68.96	5.509%	$72.759	$72.76	$72.75	$72.80
Purchase #7	$112.42	13.797%	$127.9306	$127.93	$127.95	$127.90
7 purchase totals =	$1,006.16		$1,086.4642	$1,086.46	$1,086.40	$1,086.50