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 $158.66   5.144%   $166.8215   $166.82   $166.80   $166.80  
  Purchase #2 $174.97   7.647%   $188.35   $188.35   $188.35   $188.40  
  Purchase #3 $59.94   11.571%   $66.8757   $66.88   $66.90   $66.90  
  Purchase #4 $181.40   8.666%   $197.1201   $197.12   $197.10   $197.10  
  Purchase #5 $181.69   12.862%   $205.059   $205.06   $205.05   $205.10  
  Purchase #6 $100.54   6.612%   $107.1877   $107.19   $107.20   $107.20  
  Purchase #7 $230.47   6.532%   $245.5243   $245.52   $245.50   $245.50  
  7 purchase totals = $1,087.67       $1,176.9383   $1,176.94   $1,176.90   $1,177.00