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	$119.55	11.695%	$133.5314	$133.53	$133.55	$133.50
Purchase #2	$33.87	10.723%	$37.5019	$37.50	$37.50	$37.50
Purchase #3	$45.25	13.126%	$51.1895	$51.19	$51.20	$51.20
Purchase #4	$226.94	4.121%	$236.2922	$236.29	$236.30	$236.30
Purchase #5	$220.27	3.674%	$228.3627	$228.36	$228.35	$228.40
Purchase #6	$57.68	6.357%	$61.3467	$61.35	$61.35	$61.30
Purchase #7	$213.82	7.528%	$229.9164	$229.92	$229.90	$229.90
7 purchase totals =	$917.38		$978.1408	$978.14	$978.15	$978.10