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 $103.32   10.782%   $114.46   $114.46   $114.45   $114.50  
  Purchase #2 $171.79   11.609%   $191.7331   $191.73   $191.75   $191.70  
  Purchase #3 $62.85   11.110%   $69.8326   $69.83   $69.85   $69.80  
  Purchase #4 $240.33   9.860%   $264.0265   $264.03   $264.05   $264.00  
  Purchase #5 $26.85   12.380%   $30.174   $30.17   $30.15   $30.20  
  Purchase #6 $238.87   10.401%   $263.7149   $263.71   $263.70   $263.70  
  Purchase #7 $104.65   5.797%   $110.7166   $110.72   $110.70   $110.70  
  7 purchase totals = $948.66       $1,044.6577   $1,044.65   $1,044.65   $1,044.60