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 $94.75   8.385%   $102.6948   $102.69   $102.70   $102.70  
  Purchase #2 $157.70   10.739%   $174.6354   $174.64   $174.65   $174.60  
  Purchase #3 $176.37   13.775%   $200.665   $200.67   $200.65   $200.70  
  Purchase #4 $225.85   5.291%   $237.7997   $237.80   $237.80   $237.80  
  Purchase #5 $145.25   5.530%   $153.2823   $153.28   $153.30   $153.30  
  Purchase #6 $180.83   12.618%   $203.6471   $203.65   $203.65   $203.60  
  Purchase #7 $65.30   13.618%   $74.1926   $74.19   $74.20   $74.20  
  7 purchase totals = $1,046.05       $1,146.9169   $1,146.92   $1,146.95   $1,146.90