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 $194.96   5.326%   $205.3436   $205.34   $205.35   $205.30  
  Purchase #2 $56.81   6.166%   $60.3129   $60.31   $60.30   $60.30  
  Purchase #3 $118.66   10.357%   $130.9496   $130.95   $130.95   $130.90  
  Purchase #4 $203.45   5.668%   $214.9815   $214.98   $215.00   $215.00  
  Purchase #5 $210.54   6.637%   $224.5135   $224.51   $224.50   $224.50  
  Purchase #6 $234.39   6.600%   $249.8597   $249.86   $249.85   $249.90  
  Purchase #7 $33.40   6.117%   $35.4431   $35.44   $35.45   $35.40  
  7 purchase totals = $1,052.21       $1,121.4039   $1,121.39   $1,121.40   $1,121.30