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 $88.77   8.227%   $96.0731   $96.07   $96.05   $96.10  
  Purchase #2 $126.72   4.441%   $132.3476   $132.35   $132.35   $132.30  
  Purchase #3 $105.98   10.644%   $117.2605   $117.26   $117.25   $117.30  
  Purchase #4 $216.27   13.122%   $244.6489   $244.65   $244.65   $244.60  
  Purchase #5 $210.90   5.631%   $222.7758   $222.78   $222.80   $222.80  
  Purchase #6 $180.89   12.637%   $203.7491   $203.75   $203.75   $203.70  
  Purchase #7 $173.91   3.497%   $179.9916   $179.99   $180.00   $180.00  
  7 purchase totals = $1,103.44       $1,196.8466   $1,196.85   $1,196.85   $1,196.80