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 $133.83   12.809%   $150.9723   $150.97   $150.95   $151.00  
  Purchase #2 $189.86   6.689%   $202.5597   $202.56   $202.55   $202.60  
  Purchase #3 $198.34   8.161%   $214.5265   $214.53   $214.55   $214.50  
  Purchase #4 $9.34   6.808%   $9.9759   $9.98   $10.00   $10.00  
  Purchase #5 $184.60   13.562%   $209.6355   $209.64   $209.65   $209.60  
  Purchase #6 $106.63   3.734%   $110.6116   $110.61   $110.60   $110.60  
  Purchase #7 $154.29   5.425%   $162.6602   $162.66   $162.65   $162.70  
  7 purchase totals = $976.89       $1,060.9417   $1,060.95   $1,060.95   $1,061.00