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 $175.60   11.419%   $195.6518   $195.65   $195.65   $195.70  
  Purchase #2 $244.97   11.736%   $273.7197   $273.72   $273.70   $273.70  
  Purchase #3 $165.28   7.207%   $177.1917   $177.19   $177.20   $177.20  
  Purchase #4 $155.60   6.161%   $165.1865   $165.19   $165.20   $165.20  
  Purchase #5 $8.79   13.402%   $9.968   $9.97   $9.95   $10.00  
  Purchase #6 $191.50   11.121%   $212.7967   $212.80   $212.80   $212.80  
  Purchase #7 $183.63   10.567%   $203.0342   $203.03   $203.05   $203.00  
  7 purchase totals = $1,125.37       $1,237.5486   $1,237.55   $1,237.55   $1,237.60