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 $43.40   6.791%   $46.3473   $46.35   $46.35   $46.30  
  Purchase #2 $246.58   7.172%   $264.2647   $264.26   $264.25   $264.30  
  Purchase #3 $81.76   6.667%   $87.2109   $87.21   $87.20   $87.20  
  Purchase #4 $62.56   5.686%   $66.1172   $66.12   $66.10   $66.10  
  Purchase #5 $201.93   10.244%   $222.6157   $222.62   $222.60   $222.60  
  Purchase #6 $216.37   6.732%   $230.936   $230.94   $230.95   $230.90  
  Purchase #7 $187.49   9.543%   $205.3822   $205.38   $205.40   $205.40  
  7 purchase totals = $1,040.09       $1,122.8740   $1,122.88   $1,122.85   $1,122.80