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	$54.82	12.691%	$61.7772	$61.78	$61.80	$61.80
Purchase #2	$114.43	5.238%	$120.4238	$120.42	$120.40	$120.40
Purchase #3	$194.48	5.867%	$205.8901	$205.89	$205.90	$205.90
Purchase #4	$19.53	13.288%	$22.1251	$22.13	$22.15	$22.10
Purchase #5	$160.36	5.451%	$169.1012	$169.10	$169.10	$169.10
Purchase #6	$123.63	6.646%	$131.8464	$131.85	$131.85	$131.80
Purchase #7	$184.31	3.791%	$191.2972	$191.30	$191.30	$191.30
7 purchase totals =	$851.56		$902.4610	$902.47	$902.50	$902.40