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 $55.95   7.639%   $60.224   $60.22   $60.20   $60.20  
  Purchase #2 $209.36   11.168%   $232.7413   $232.74   $232.75   $232.70  
  Purchase #3 $243.98   7.250%   $261.6686   $261.67   $261.65   $261.70  
  Purchase #4 $55.67   3.558%   $57.6507   $57.65   $57.65   $57.70  
  Purchase #5 $80.32   10.832%   $89.0203   $89.02   $89.00   $89.00  
  Purchase #6 $208.49   7.665%   $224.4708   $224.47   $224.45   $224.50  
  Purchase #7 $239.32   6.793%   $255.577   $255.58   $255.60   $255.60  
  7 purchase totals = $1,093.09       $1,181.3527   $1,181.35   $1,181.30   $1,181.40