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 $82.31   13.590%   $93.4959   $93.50   $93.50   $93.50  
  Purchase #2 $5.58   6.616%   $5.9492   $5.95   $5.95   $5.90  
  Purchase #3 $146.95   4.728%   $153.8978   $153.90   $153.90   $153.90  
  Purchase #4 $224.44   4.250%   $233.9787   $233.98   $234.00   $234.00  
  Purchase #5 $166.42   3.631%   $172.4627   $172.46   $172.45   $172.50  
  Purchase #6 $233.43   10.639%   $258.2646   $258.26   $258.25   $258.30  
  Purchase #7 $203.58   11.603%   $227.2014   $227.20   $227.20   $227.20  
  7 purchase totals = $1,062.71       $1,145.2503   $1,145.25   $1,145.25   $1,145.30