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	$73.61	11.579%	$82.1333	$82.13	$82.15	$82.10
Purchase #2	$143.78	6.378%	$152.9503	$152.95	$152.95	$153.00
Purchase #3	$214.27	12.281%	$240.5845	$240.58	$240.60	$240.60
Purchase #4	$80.30	6.619%	$85.6151	$85.62	$85.60	$85.60
Purchase #5	$213.52	7.765%	$230.0998	$230.10	$230.10	$230.10
Purchase #6	$110.39	5.402%	$116.3533	$116.35	$116.35	$116.40
Purchase #7	$164.47	9.395%	$179.922	$179.92	$179.90	$179.90
7 purchase totals =	$1,000.34		$1,087.6583	$1,087.65	$1,087.65	$1,087.70