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 $119.74   3.341%   $123.7405   $123.74   $123.75   $123.70  
  Purchase #2 $203.29   13.806%   $231.3562   $231.36   $231.35   $231.40  
  Purchase #3 $33.25   5.839%   $35.1915   $35.19   $35.20   $35.20  
  Purchase #4 $245.61   5.355%   $258.7624   $258.76   $258.75   $258.80  
  Purchase #5 $16.52   7.358%   $17.7355   $17.74   $17.75   $17.70  
  Purchase #6 $178.91   5.734%   $189.1687   $189.17   $189.15   $189.20  
  Purchase #7 $196.46   4.253%   $204.8154   $204.82   $204.80   $204.80  
  7 purchase totals = $993.78       $1,060.7702   $1,060.78   $1,060.75   $1,060.80