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 $91.56   4.532%   $95.7095   $95.71   $95.70   $95.70  
  Purchase #2 $182.31   13.486%   $206.8963   $206.90   $206.90   $206.90  
  Purchase #3 $124.49   9.631%   $136.4796   $136.48   $136.50   $136.50  
  Purchase #4 $95.31   12.644%   $107.361   $107.36   $107.35   $107.40  
  Purchase #5 $170.77   8.298%   $184.9405   $184.94   $184.95   $184.90  
  Purchase #6 $173.49   12.148%   $194.5656   $194.57   $194.55   $194.60  
  Purchase #7 $191.31   6.446%   $203.6418   $203.64   $203.65   $203.60  
  7 purchase totals = $1,029.24       $1,129.5943   $1,129.60   $1,129.60   $1,129.60