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	$241.39	8.357%	$261.563	$261.56	$261.55	$261.60
Purchase #2	$139.51	9.224%	$152.3784	$152.38	$152.40	$152.40
Purchase #3	$163.28	6.237%	$173.4638	$173.46	$173.45	$173.50
Purchase #4	$18.42	10.767%	$20.4033	$20.40	$20.40	$20.40
Purchase #5	$232.91	5.221%	$245.0702	$245.07	$245.05	$245.10
Purchase #6	$94.46	7.286%	$101.3424	$101.34	$101.35	$101.30
Purchase #7	$69.69	4.156%	$72.5863	$72.59	$72.60	$72.60
7 purchase totals =	$959.66		$1,026.8074	$1,026.80	$1,026.80	$1,026.90