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 $94.55   8.143%   $102.2492   $102.25   $102.25   $102.20  
  Purchase #2 $169.29   10.576%   $187.1941   $187.19   $187.20   $187.20  
  Purchase #3 $225.96   6.797%   $241.3185   $241.32   $241.30   $241.30  
  Purchase #4 $22.41   10.124%   $24.6788   $24.68   $24.70   $24.70  
  Purchase #5 $42.41   8.601%   $46.0577   $46.06   $46.05   $46.10  
  Purchase #6 $23.84   7.251%   $25.5686   $25.57   $25.55   $25.60  
  Purchase #7 $242.39   11.112%   $269.3244   $269.32   $269.30   $269.30  
  7 purchase totals = $820.85       $896.3913   $896.39   $896.35   $896.40