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 $75.86   8.564%   $82.3567   $82.36   $82.35   $82.40  
  Purchase #2 $224.52   3.303%   $231.9359   $231.94   $231.95   $231.90  
  Purchase #3 $210.77   7.127%   $225.7916   $225.79   $225.80   $225.80  
  Purchase #4 $149.99   12.619%   $168.9172   $168.92   $168.90   $168.90  
  Purchase #5 $224.32   13.628%   $254.8903   $254.89   $254.90   $254.90  
  Purchase #6 $93.98   10.635%   $103.9748   $103.97   $103.95   $104.00  
  Purchase #7 $82.67   13.177%   $93.5634   $93.56   $93.55   $93.60  
  7 purchase totals = $1,062.11       $1,161.4299   $1,161.43   $1,161.40   $1,161.50