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 $112.79   11.444%   $125.6977   $125.70   $125.70   $125.70  
  Purchase #2 $144.59   6.301%   $153.7006   $153.70   $153.70   $153.70  
  Purchase #3 $227.47   8.167%   $246.0475   $246.05   $246.05   $246.00  
  Purchase #4 $161.78   3.216%   $166.9828   $166.98   $167.00   $167.00  
  Purchase #5 $120.78   6.238%   $128.3143   $128.31   $128.30   $128.30  
  Purchase #6 $179.92   12.810%   $202.9678   $202.97   $202.95   $203.00  
  Purchase #7 $76.83   13.127%   $86.9155   $86.92   $86.90   $86.90  
  7 purchase totals = $1,024.16       $1,110.6262   $1,110.63   $1,110.60   $1,110.60