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 $70.53   4.140%   $73.4499   $73.45   $73.45   $73.40  
  Purchase #2 $234.57   4.418%   $244.9333   $244.93   $244.95   $244.90  
  Purchase #3 $187.99   12.816%   $212.0828   $212.08   $212.10   $212.10  
  Purchase #4 $209.72   6.872%   $224.132   $224.13   $224.15   $224.10  
  Purchase #5 $36.76   6.795%   $39.2578   $39.26   $39.25   $39.30  
  Purchase #6 $14.97   4.718%   $15.6763   $15.68   $15.70   $15.70  
  Purchase #7 $217.39   12.794%   $245.2029   $245.20   $245.20   $245.20  
  7 purchase totals = $971.93       $1,054.7350   $1,054.73   $1,054.80   $1,054.70