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 $175.97   12.257%   $197.5386   $197.54   $197.55   $197.50  
  Purchase #2 $220.95   13.842%   $251.5339   $251.53   $251.55   $251.50  
  Purchase #3 $164.31   6.443%   $174.8965   $174.90   $174.90   $174.90  
  Purchase #4 $16.58   8.192%   $17.9382   $17.94   $17.95   $17.90  
  Purchase #5 $247.82   11.637%   $276.6588   $276.66   $276.65   $276.70  
  Purchase #6 $130.88   11.581%   $146.0372   $146.04   $146.05   $146.00  
  Purchase #7 $35.60   5.413%   $37.527   $37.53   $37.55   $37.50  
  7 purchase totals = $992.11       $1,102.1302   $1,102.14   $1,102.20   $1,102.00