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	$187.53	11.585%	$209.2554	$209.26	$209.25	$209.30
Purchase #2	$171.94	11.418%	$191.5721	$191.57	$191.55	$191.60
Purchase #3	$136.99	4.295%	$142.8737	$142.87	$142.85	$142.90
Purchase #4	$16.99	8.110%	$18.3679	$18.37	$18.35	$18.40
Purchase #5	$136.47	5.411%	$143.8544	$143.85	$143.85	$143.90
Purchase #6	$217.42	12.167%	$243.8735	$243.87	$243.85	$243.90
Purchase #7	$150.83	8.784%	$164.0789	$164.08	$164.10	$164.10
7 purchase totals =	$1,018.17		$1,113.8759	$1,113.87	$1,113.80	$1,114.10