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 $247.82   6.602%   $264.1811   $264.18   $264.20   $264.20  
  Purchase #2 $118.92   8.728%   $129.2993   $129.30   $129.30   $129.30  
  Purchase #3 $85.72   5.668%   $90.5786   $90.58   $90.60   $90.60  
  Purchase #4 $38.86   5.102%   $40.8426   $40.84   $40.85   $40.80  
  Purchase #5 $146.94   6.558%   $156.5763   $156.58   $156.60   $156.60  
  Purchase #6 $189.94   11.838%   $212.4251   $212.43   $212.45   $212.40  
  Purchase #7 $180.76   11.284%   $201.157   $201.16   $201.15   $201.20  
  7 purchase totals = $1,008.96       $1,095.0600   $1,095.07   $1,095.15   $1,095.10