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 $139.86   8.677%   $151.9957   $152.00   $152.00   $152.00  
  Purchase #2 $170.98   8.266%   $185.1132   $185.11   $185.10   $185.10  
  Purchase #3 $117.95   10.398%   $130.2144   $130.21   $130.20   $130.20  
  Purchase #4 $239.95   10.524%   $265.2023   $265.20   $265.20   $265.20  
  Purchase #5 $56.50   6.207%   $60.007   $60.01   $60.00   $60.00  
  Purchase #6 $150.47   6.688%   $160.5334   $160.53   $160.55   $160.50  
  Purchase #7 $231.78   4.569%   $242.37   $242.37   $242.35   $242.40  
  7 purchase totals = $1,107.49       $1,195.4360   $1,195.43   $1,195.40   $1,195.40