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	$180.39	4.153%	$187.8816	$187.88	$187.90	$187.90
Purchase #2	$119.63	7.257%	$128.3115	$128.31	$128.30	$128.30
Purchase #3	$209.90	8.182%	$227.074	$227.07	$227.05	$227.10
Purchase #4	$63.30	8.803%	$68.8723	$68.87	$68.85	$68.90
Purchase #5	$138.36	13.346%	$156.8255	$156.83	$156.85	$156.80
Purchase #6	$90.54	10.521%	$100.0657	$100.07	$100.05	$100.10
Purchase #7	$207.28	13.602%	$235.4742	$235.47	$235.45	$235.50
7 purchase totals =	$1,009.40		$1,104.5048	$1,104.50	$1,104.45	$1,104.60