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 $58.54   5.661%   $61.8539   $61.85   $61.85   $61.90  
  Purchase #2 $195.34   12.412%   $219.5856   $219.59   $219.60   $219.60  
  Purchase #3 $169.72   7.138%   $181.8346   $181.83   $181.85   $181.80  
  Purchase #4 $184.88   12.245%   $207.5186   $207.52   $207.50   $207.50  
  Purchase #5 $73.69   13.491%   $83.6315   $83.63   $83.65   $83.60  
  Purchase #6 $179.31   13.185%   $202.952   $202.95   $202.95   $203.00  
  Purchase #7 $250.66   13.205%   $283.7597   $283.76   $283.75   $283.80  
  7 purchase totals = $1,112.14       $1,241.1359   $1,241.13   $1,241.15   $1,241.20