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 $196.69   3.134%   $202.8543   $202.85   $202.85   $202.90  
  Purchase #2 $244.95   13.332%   $277.6067   $277.61   $277.60   $277.60  
  Purchase #3 $5.28   3.508%   $5.4652   $5.47   $5.45   $5.50  
  Purchase #4 $203.32   6.841%   $217.2291   $217.23   $217.25   $217.20  
  Purchase #5 $78.84   4.594%   $82.4619   $82.46   $82.45   $82.50  
  Purchase #6 $215.27   5.366%   $226.8214   $226.82   $226.80   $226.80  
  Purchase #7 $72.36   11.347%   $80.5707   $80.57   $80.55   $80.60  
  7 purchase totals = $1,016.71       $1,093.0093   $1,093.01   $1,092.95   $1,093.10