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	$218.58	7.341%	$234.626	$234.63	$234.65	$234.60
Purchase #2	$243.29	12.725%	$274.2487	$274.25	$274.25	$274.20
Purchase #3	$61.63	9.676%	$67.5933	$67.59	$67.60	$67.60
Purchase #4	$45.33	10.854%	$50.2501	$50.25	$50.25	$50.30
Purchase #5	$61.96	12.103%	$69.459	$69.46	$69.45	$69.50
Purchase #6	$248.97	9.451%	$272.5002	$272.50	$272.50	$272.50
Purchase #7	$75.83	8.585%	$82.34	$82.34	$82.35	$82.30
7 purchase totals =	$955.59		$1,051.0173	$1,051.02	$1,051.05	$1,051.00