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 $207.93   7.106%   $222.7055   $222.71   $222.70   $222.70  
  Purchase #2 $197.66   10.119%   $217.6612   $217.66   $217.65   $217.70  
  Purchase #3 $206.73   11.644%   $230.8016   $230.80   $230.80   $230.80  
  Purchase #4 $174.97   4.298%   $182.4902   $182.49   $182.50   $182.50  
  Purchase #5 $45.79   12.711%   $51.6104   $51.61   $51.60   $51.60  
  Purchase #6 $5.25   7.658%   $5.652   $5.65   $5.65   $5.70  
  Purchase #7 $137.48   9.350%   $150.3344   $150.33   $150.35   $150.30  
  7 purchase totals = $975.81       $1,061.2553   $1,061.25   $1,061.25   $1,061.30