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 $61.49   10.841%   $68.1561   $68.16   $68.15   $68.20  
  Purchase #2 $246.62   11.666%   $275.3907   $275.39   $275.40   $275.40  
  Purchase #3 $178.31   12.444%   $200.4989   $200.50   $200.50   $200.50  
  Purchase #4 $157.91   8.299%   $171.015   $171.02   $171.00   $171.00  
  Purchase #5 $152.40   13.296%   $172.6631   $172.66   $172.65   $172.70  
  Purchase #6 $6.29   9.246%   $6.8716   $6.87   $6.85   $6.90  
  Purchase #7 $55.45   9.744%   $60.853   $60.85   $60.85   $60.90  
  7 purchase totals = $858.47       $955.4484   $955.45   $955.40   $955.60