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 $196.77   4.449%   $205.5243   $205.52   $205.50   $205.50  
  Purchase #2 $33.60   4.209%   $35.0142   $35.01   $35.00   $35.00  
  Purchase #3 $53.55   5.674%   $56.5884   $56.59   $56.60   $56.60  
  Purchase #4 $211.39   6.263%   $224.6294   $224.63   $224.65   $224.60  
  Purchase #5 $235.82   9.389%   $257.9611   $257.96   $257.95   $258.00  
  Purchase #6 $95.87   5.354%   $101.0029   $101.00   $101.00   $101.00  
  Purchase #7 $181.66   11.309%   $202.2039   $202.20   $202.20   $202.20  
  7 purchase totals = $1,008.66       $1,082.9242   $1,082.91   $1,082.90   $1,082.90