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 $74.47   12.658%   $83.8964   $83.90   $83.90   $83.90  
  Purchase #2 $158.31   4.864%   $166.0102   $166.01   $166.00   $166.00  
  Purchase #3 $97.81   12.442%   $109.9795   $109.98   $110.00   $110.00  
  Purchase #4 $144.44   7.435%   $155.1791   $155.18   $155.20   $155.20  
  Purchase #5 $215.65   3.841%   $223.9331   $223.93   $223.95   $223.90  
  Purchase #6 $169.97   13.818%   $193.4565   $193.46   $193.45   $193.50  
  Purchase #7 $245.27   7.115%   $262.721   $262.72   $262.70   $262.70  
  7 purchase totals = $1,105.92       $1,195.1758   $1,195.18   $1,195.20   $1,195.20