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	$219.37	12.488%	$246.7649	$246.76	$246.75	$246.80
Purchase #2	$148.60	10.673%	$164.4601	$164.46	$164.45	$164.50
Purchase #3	$168.52	7.716%	$181.523	$181.52	$181.50	$181.50
Purchase #4	$39.61	8.780%	$43.0878	$43.09	$43.10	$43.10
Purchase #5	$84.84	8.586%	$92.1244	$92.12	$92.10	$92.10
Purchase #6	$220.69	11.713%	$246.5394	$246.54	$246.55	$246.50
Purchase #7	$198.78	5.399%	$209.5121	$209.51	$209.50	$209.50
7 purchase totals =	$1,080.41		$1,184.0117	$1,184.00	$1,183.95	$1,184.00