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	$234.75	9.107%	$256.1287	$256.13	$256.15	$256.10
Purchase #2	$222.38	9.854%	$244.2933	$244.29	$244.30	$244.30
Purchase #3	$90.27	4.160%	$94.0252	$94.03	$94.05	$94.00
Purchase #4	$201.77	5.617%	$213.1034	$213.10	$213.10	$213.10
Purchase #5	$22.39	9.436%	$24.5027	$24.50	$24.50	$24.50
Purchase #6	$154.92	9.391%	$169.4685	$169.47	$169.45	$169.50
Purchase #7	$141.37	6.328%	$150.3159	$150.32	$150.30	$150.30
7 purchase totals =	$1,067.85		$1,151.8377	$1,151.84	$1,151.85	$1,151.80