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 $162.52   8.865%   $176.9274   $176.93   $176.95   $176.90  
  Purchase #2 $174.91   11.873%   $195.6771   $195.68   $195.70   $195.70  
  Purchase #3 $158.77   7.443%   $170.5873   $170.59   $170.60   $170.60  
  Purchase #4 $122.96   8.441%   $133.3391   $133.34   $133.35   $133.30  
  Purchase #5 $52.44   7.544%   $56.3961   $56.40   $56.40   $56.40  
  Purchase #6 $184.85   8.731%   $200.9893   $200.99   $201.00   $201.00  
  Purchase #7 $146.42   12.667%   $164.967   $164.97   $164.95   $165.00  
  7 purchase totals = $1,002.87       $1,098.8833   $1,098.90   $1,098.95   $1,098.90