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 $93.31   11.173%   $103.7355   $103.74   $103.75   $103.70  
  Purchase #2 $224.49   4.326%   $234.2014   $234.20   $234.20   $234.20  
  Purchase #3 $43.34   11.325%   $48.2483   $48.25   $48.25   $48.20  
  Purchase #4 $76.38   8.220%   $82.6584   $82.66   $82.65   $82.70  
  Purchase #5 $238.32   13.589%   $270.7053   $270.71   $270.70   $270.70  
  Purchase #6 $194.69   9.753%   $213.6781   $213.68   $213.70   $213.70  
  Purchase #7 $85.92   10.302%   $94.7715   $94.77   $94.75   $94.80  
  7 purchase totals = $956.45       $1,047.9985   $1,048.01   $1,048.00   $1,048.00