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	$217.43	12.362%	$244.3087	$244.31	$244.30	$244.30
Purchase #2	$231.80	10.203%	$255.4506	$255.45	$255.45	$255.50
Purchase #3	$156.70	10.341%	$172.9043	$172.90	$172.90	$172.90
Purchase #4	$46.48	10.619%	$51.4157	$51.42	$51.40	$51.40
Purchase #5	$84.59	9.304%	$92.4603	$92.46	$92.45	$92.50
Purchase #6	$52.92	8.537%	$57.4378	$57.44	$57.45	$57.40
Purchase #7	$231.52	6.105%	$245.6543	$245.65	$245.65	$245.70
7 purchase totals =	$1,021.44		$1,119.6317	$1,119.63	$1,119.60	$1,119.70