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	$162.47	6.277%	$172.6682	$172.67	$172.65	$172.70
Purchase #2	$119.50	3.617%	$123.8223	$123.82	$123.80	$123.80
Purchase #3	$205.90	3.194%	$212.4764	$212.48	$212.50	$212.50
Purchase #4	$19.63	10.437%	$21.6788	$21.68	$21.70	$21.70
Purchase #5	$120.31	12.615%	$135.4871	$135.49	$135.50	$135.50
Purchase #6	$132.46	6.648%	$141.2659	$141.27	$141.25	$141.30
Purchase #7	$172.39	8.742%	$187.4603	$187.46	$187.45	$187.50
7 purchase totals =	$932.66		$994.8590	$994.87	$994.85	$995.00