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	$232.50	11.318%	$258.8144	$258.81	$258.80	$258.80
Purchase #2	$241.48	5.711%	$255.2709	$255.27	$255.25	$255.30
Purchase #3	$39.39	3.493%	$40.7659	$40.77	$40.75	$40.80
Purchase #4	$29.45	13.710%	$33.4876	$33.49	$33.50	$33.50
Purchase #5	$168.63	10.600%	$186.5048	$186.50	$186.50	$186.50
Purchase #6	$243.68	7.252%	$261.3517	$261.35	$261.35	$261.40
Purchase #7	$29.82	13.232%	$33.7658	$33.77	$33.75	$33.80
7 purchase totals =	$984.95		$1,069.9611	$1,069.96	$1,069.90	$1,070.10