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 $90.70   5.406%   $95.6032   $95.60   $95.60   $95.60  
  Purchase #2 $149.83   6.424%   $159.4551   $159.46   $159.45   $159.50  
  Purchase #3 $9.30   4.700%   $9.7371   $9.74   $9.75   $9.70  
  Purchase #4 $192.31   6.596%   $204.9948   $204.99   $205.00   $205.00  
  Purchase #5 $69.85   5.113%   $73.4214   $73.42   $73.40   $73.40  
  Purchase #6 $110.93   10.331%   $122.3902   $122.39   $122.40   $122.40  
  Purchase #7 $53.64   12.375%   $60.278   $60.28   $60.30   $60.30  
  7 purchase totals = $676.56       $725.8798   $725.88   $725.90   $725.90