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	$241.32	9.660%	$264.6315	$264.63	$264.65	$264.60
Purchase #2	$196.46	11.760%	$219.5637	$219.56	$219.55	$219.60
Purchase #3	$139.69	5.301%	$147.095	$147.10	$147.10	$147.10
Purchase #4	$78.32	11.685%	$87.4717	$87.47	$87.45	$87.50
Purchase #5	$193.63	12.429%	$217.6963	$217.70	$217.70	$217.70
Purchase #6	$168.92	10.490%	$186.6397	$186.64	$186.65	$186.60
Purchase #7	$99.59	6.211%	$105.7755	$105.78	$105.80	$105.80
7 purchase totals =	$1,117.93		$1,228.8734	$1,228.88	$1,228.90	$1,228.90