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	$235.59	10.230%	$259.6909	$259.69	$259.70	$259.70
Purchase #2	$80.45	8.474%	$87.2673	$87.27	$87.25	$87.30
Purchase #3	$125.68	13.472%	$142.6116	$142.61	$142.60	$142.60
Purchase #4	$196.68	10.543%	$217.416	$217.42	$217.40	$217.40
Purchase #5	$156.51	10.478%	$172.9091	$172.91	$172.90	$172.90
Purchase #6	$238.86	3.199%	$246.5011	$246.50	$246.50	$246.50
Purchase #7	$10.48	9.344%	$11.4593	$11.46	$11.45	$11.50
7 purchase totals =	$1,044.25		$1,137.8553	$1,137.86	$1,137.80	$1,137.90