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	$169.34	7.285%	$181.6764	$181.68	$181.70	$181.70
Purchase #2	$58.43	11.708%	$65.271	$65.27	$65.25	$65.30
Purchase #3	$228.95	6.323%	$243.4265	$243.43	$243.45	$243.40
Purchase #4	$100.57	4.770%	$105.3672	$105.37	$105.35	$105.40
Purchase #5	$220.92	7.768%	$238.0811	$238.08	$238.10	$238.10
Purchase #6	$66.72	8.306%	$72.2618	$72.26	$72.25	$72.30
Purchase #7	$164.89	4.542%	$172.3793	$172.38	$172.40	$172.40
7 purchase totals =	$1,009.82		$1,078.4633	$1,078.47	$1,078.50	$1,078.60