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	$94.35	10.554%	$104.3077	$104.31	$104.30	$104.30
Purchase #2	$123.64	11.626%	$138.0144	$138.01	$138.00	$138.00
Purchase #3	$151.94	10.419%	$167.7706	$167.77	$167.75	$167.80
Purchase #4	$93.94	11.738%	$104.9667	$104.97	$104.95	$105.00
Purchase #5	$231.94	7.739%	$249.8898	$249.89	$249.90	$249.90
Purchase #6	$48.88	13.136%	$55.3009	$55.30	$55.30	$55.30
Purchase #7	$130.36	12.683%	$146.8936	$146.89	$146.90	$146.90
7 purchase totals =	$875.05		$967.1437	$967.14	$967.10	$967.20