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 $195.30   5.303%   $205.6568   $205.66   $205.65   $205.70  
  Purchase #2 $29.31   11.392%   $32.649   $32.65   $32.65   $32.60  
  Purchase #3 $220.82   12.114%   $247.5701   $247.57   $247.55   $247.60  
  Purchase #4 $130.80   10.526%   $144.568   $144.57   $144.55   $144.60  
  Purchase #5 $204.81   10.626%   $226.5731   $226.57   $226.55   $226.60  
  Purchase #6 $112.32   11.315%   $125.029   $125.03   $125.05   $125.00  
  Purchase #7 $74.37   8.722%   $80.8566   $80.86   $80.85   $80.90  
  7 purchase totals = $967.73       $1,062.9026   $1,062.91   $1,062.85   $1,063.00