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 $59.36   9.553%   $65.0307   $65.03   $65.05   $65.00  
  Purchase #2 $162.45   9.637%   $178.1053   $178.11   $178.10   $178.10  
  Purchase #3 $113.32   5.342%   $119.3736   $119.37   $119.35   $119.40  
  Purchase #4 $246.57   6.117%   $261.6527   $261.65   $261.65   $261.70  
  Purchase #5 $213.91   12.484%   $240.6145   $240.61   $240.60   $240.60  
  Purchase #6 $211.35   6.847%   $225.8211   $225.82   $225.80   $225.80  
  Purchase #7 $31.74   7.511%   $34.124   $34.12   $34.10   $34.10  
  7 purchase totals = $1,038.70       $1,124.7219   $1,124.71   $1,124.65   $1,124.70