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 $124.33   6.673%   $132.6265   $132.63   $132.65   $132.60  
  Purchase #2 $88.61   12.685%   $99.8502   $99.85   $99.85   $99.90  
  Purchase #3 $84.39   12.710%   $95.116   $95.12   $95.10   $95.10  
  Purchase #4 $203.69   11.654%   $227.428   $227.43   $227.45   $227.40  
  Purchase #5 $170.75   6.317%   $181.5363   $181.54   $181.55   $181.50  
  Purchase #6 $115.97   3.361%   $119.8678   $119.87   $119.85   $119.90  
  Purchase #7 $159.29   10.239%   $175.5997   $175.60   $175.60   $175.60  
  7 purchase totals = $947.03       $1,032.0245   $1,032.04   $1,032.05   $1,032.00