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	$108.34	9.789%	$118.9454	$118.95	$118.95	$118.90
Purchase #2	$96.50	12.252%	$108.3232	$108.32	$108.30	$108.30
Purchase #3	$224.50	8.454%	$243.4792	$243.48	$243.50	$243.50
Purchase #4	$59.95	13.291%	$67.918	$67.92	$67.90	$67.90
Purchase #5	$220.82	9.237%	$241.2171	$241.22	$241.20	$241.20
Purchase #6	$72.39	13.213%	$81.9549	$81.95	$81.95	$82.00
Purchase #7	$222.35	5.489%	$234.5548	$234.55	$234.55	$234.60
7 purchase totals =	$1,004.85		$1,096.3926	$1,096.39	$1,096.35	$1,096.40