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 $86.54   10.557%   $95.676   $95.68   $95.70   $95.70  
  Purchase #2 $203.53   13.175%   $230.3451   $230.35   $230.35   $230.30  
  Purchase #3 $233.99   11.206%   $260.2109   $260.21   $260.20   $260.20  
  Purchase #4 $29.58   10.793%   $32.7726   $32.77   $32.75   $32.80  
  Purchase #5 $131.95   11.297%   $146.8564   $146.86   $146.85   $146.90  
  Purchase #6 $119.65   5.736%   $126.5131   $126.51   $126.50   $126.50  
  Purchase #7 $247.35   7.376%   $265.5945   $265.59   $265.60   $265.60  
  7 purchase totals = $1,052.59       $1,157.9686   $1,157.97   $1,157.95   $1,158.00