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	$233.40	9.821%	$256.3222	$256.32	$256.30	$256.30
Purchase #2	$220.38	5.222%	$231.8882	$231.89	$231.90	$231.90
Purchase #3	$228.87	8.799%	$249.0083	$249.01	$249.00	$249.00
Purchase #4	$35.53	13.410%	$40.2946	$40.29	$40.30	$40.30
Purchase #5	$94.78	5.500%	$99.9929	$99.99	$100.00	$100.00
Purchase #6	$40.74	12.602%	$45.8741	$45.87	$45.85	$45.90
Purchase #7	$118.66	10.401%	$131.0018	$131.00	$131.00	$131.00
7 purchase totals =	$972.36		$1,054.3821	$1,054.37	$1,054.35	$1,054.40