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	$229.84	13.716%	$261.3649	$261.36	$261.35	$261.40
Purchase #2	$82.35	8.158%	$89.0681	$89.07	$89.05	$89.10
Purchase #3	$59.74	7.575%	$64.2653	$64.27	$64.25	$64.30
Purchase #4	$53.94	13.734%	$61.3481	$61.35	$61.35	$61.30
Purchase #5	$34.29	8.803%	$37.3085	$37.31	$37.30	$37.30
Purchase #6	$162.89	9.830%	$178.9021	$178.90	$178.90	$178.90
Purchase #7	$92.60	10.555%	$102.3739	$102.37	$102.35	$102.40
7 purchase totals =	$715.65		$794.6309	$794.63	$794.55	$794.70