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	$139.53	3.207%	$144.0047	$144.00	$144.00	$144.00
Purchase #2	$170.83	11.472%	$190.4276	$190.43	$190.45	$190.40
Purchase #3	$231.78	4.789%	$242.8799	$242.88	$242.90	$242.90
Purchase #4	$211.88	7.180%	$227.093	$227.09	$227.10	$227.10
Purchase #5	$123.49	3.105%	$127.3244	$127.32	$127.30	$127.30
Purchase #6	$91.84	12.273%	$103.1115	$103.11	$103.10	$103.10
Purchase #7	$61.49	13.672%	$69.8969	$69.90	$69.90	$69.90
7 purchase totals =	$1,030.84		$1,104.7380	$1,104.73	$1,104.75	$1,104.70