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 $193.93   5.269%   $204.1482   $204.15   $204.15   $204.10  
  Purchase #2 $178.32   9.615%   $195.4655   $195.47   $195.45   $195.50  
  Purchase #3 $56.73   5.653%   $59.9369   $59.94   $59.95   $59.90  
  Purchase #4 $66.99   8.302%   $72.5515   $72.55   $72.55   $72.60  
  Purchase #5 $210.78   4.445%   $220.1492   $220.15   $220.15   $220.10  
  Purchase #6 $66.60   3.731%   $69.0848   $69.08   $69.10   $69.10  
  Purchase #7 $219.88   5.356%   $231.6568   $231.66   $231.65   $231.70  
  7 purchase totals = $993.23       $1,052.9929   $1,053.00   $1,053.00   $1,053.00