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 $59.56   5.488%   $62.8287   $62.83   $62.85   $62.80  
  Purchase #2 $130.62   4.400%   $136.3673   $136.37   $136.35   $136.40  
  Purchase #3 $133.28   12.825%   $150.3732   $150.37   $150.35   $150.40  
  Purchase #4 $119.29   4.614%   $124.794   $124.79   $124.80   $124.80  
  Purchase #5 $219.65   6.147%   $233.1519   $233.15   $233.15   $233.20  
  Purchase #6 $179.37   8.666%   $194.9142   $194.91   $194.90   $194.90  
  Purchase #7 $144.76   8.825%   $157.5351   $157.54   $157.55   $157.50  
  7 purchase totals = $986.53       $1,059.9644   $1,059.96   $1,059.95   $1,060.00