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 $175.33   11.227%   $195.0143   $195.01   $195.00   $195.00  
  Purchase #2 $58.59   10.822%   $64.9306   $64.93   $64.95   $64.90  
  Purchase #3 $63.72   10.691%   $70.5323   $70.53   $70.55   $70.50  
  Purchase #4 $198.79   12.731%   $224.098   $224.10   $224.10   $224.10  
  Purchase #5 $246.88   13.232%   $279.5472   $279.55   $279.55   $279.50  
  Purchase #6 $133.67   7.162%   $143.2434   $143.24   $143.25   $143.20  
  Purchase #7 $32.99   13.410%   $37.414   $37.41   $37.40   $37.40  
  7 purchase totals = $909.97       $1,014.7798   $1,014.77   $1,014.80   $1,014.60