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	$232.91	10.143%	$256.5341	$256.53	$256.55	$256.50
Purchase #2	$185.46	13.684%	$210.8383	$210.84	$210.85	$210.80
Purchase #3	$53.33	5.505%	$56.2658	$56.27	$56.25	$56.30
Purchase #4	$165.90	3.680%	$172.0051	$172.01	$172.00	$172.00
Purchase #5	$41.74	5.327%	$43.9635	$43.96	$43.95	$44.00
Purchase #6	$62.49	10.555%	$69.0858	$69.09	$69.10	$69.10
Purchase #7	$197.59	12.757%	$222.7966	$222.80	$222.80	$222.80
7 purchase totals =	$939.42		$1,031.4892	$1,031.50	$1,031.50	$1,031.50