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 $58.52   5.782%   $61.9036   $61.90   $61.90   $61.90  
  Purchase #2 $75.78   6.413%   $80.6398   $80.64   $80.65   $80.60  
  Purchase #3 $11.81   8.585%   $12.8239   $12.82   $12.80   $12.80  
  Purchase #4 $141.92   3.254%   $146.5381   $146.54   $146.55   $146.50  
  Purchase #5 $21.77   13.432%   $24.6941   $24.69   $24.70   $24.70  
  Purchase #6 $122.29   9.510%   $133.9198   $133.92   $133.90   $133.90  
  Purchase #7 $232.98   3.520%   $241.1809   $241.18   $241.20   $241.20  
  7 purchase totals = $665.07       $701.7002   $701.69   $701.70   $701.60