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	$245.54	4.585%	$256.798	$256.80	$256.80	$256.80
Purchase #2	$60.27	12.154%	$67.5952	$67.60	$67.60	$67.60
Purchase #3	$153.61	7.756%	$165.524	$165.52	$165.50	$165.50
Purchase #4	$86.67	13.521%	$98.3887	$98.39	$98.40	$98.40
Purchase #5	$92.38	5.724%	$97.6678	$97.67	$97.65	$97.70
Purchase #6	$93.76	8.167%	$101.4174	$101.42	$101.40	$101.40
Purchase #7	$208.76	3.437%	$215.9351	$215.94	$215.95	$215.90
7 purchase totals =	$940.99		$1,003.3262	$1,003.34	$1,003.30	$1,003.30