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 $82.77   5.158%   $87.0393   $87.04   $87.05   $87.00  
  Purchase #2 $118.72   12.735%   $133.839   $133.84   $133.85   $133.80  
  Purchase #3 $170.69   3.496%   $176.6573   $176.66   $176.65   $176.70  
  Purchase #4 $222.99   10.290%   $245.9357   $245.94   $245.95   $245.90  
  Purchase #5 $182.96   10.446%   $202.072   $202.07   $202.05   $202.10  
  Purchase #6 $140.93   10.354%   $155.5219   $155.52   $155.50   $155.50  
  Purchase #7 $184.87   9.608%   $202.6323   $202.63   $202.65   $202.60  
  7 purchase totals = $1,103.93       $1,203.6975   $1,203.70   $1,203.70   $1,203.60