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	$227.48	13.213%	$257.5369	$257.54	$257.55	$257.50
Purchase #2	$113.50	11.709%	$126.7897	$126.79	$126.80	$126.80
Purchase #3	$48.87	7.205%	$52.3911	$52.39	$52.40	$52.40
Purchase #4	$198.35	12.372%	$222.8899	$222.89	$222.90	$222.90
Purchase #5	$150.34	10.596%	$166.27	$166.27	$166.25	$166.30
Purchase #6	$205.38	7.381%	$220.5391	$220.54	$220.55	$220.50
Purchase #7	$35.47	6.748%	$37.8635	$37.86	$37.85	$37.90
7 purchase totals =	$979.39		$1,084.2802	$1,084.28	$1,084.30	$1,084.30