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 $69.51   10.481%   $76.7953   $76.80   $76.80   $76.80  
  Purchase #2 $132.91   6.118%   $141.0414   $141.04   $141.05   $141.00  
  Purchase #3 $181.91   8.190%   $196.8084   $196.81   $196.80   $196.80  
  Purchase #4 $10.86   7.208%   $11.6428   $11.64   $11.65   $11.60  
  Purchase #5 $48.38   4.282%   $50.4516   $50.45   $50.45   $50.50  
  Purchase #6 $160.92   8.540%   $174.6626   $174.66   $174.65   $174.70  
  Purchase #7 $97.94   4.777%   $102.6186   $102.62   $102.60   $102.60  
  7 purchase totals = $702.43       $754.0207   $754.02   $754.00   $754.00