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 $153.65   5.592%   $162.2421   $162.24   $162.25   $162.20  
  Purchase #2 $59.93   7.287%   $64.2971   $64.30   $64.30   $64.30  
  Purchase #3 $14.66   13.207%   $16.5961   $16.60   $16.60   $16.60  
  Purchase #4 $216.64   13.582%   $246.064   $246.06   $246.05   $246.10  
  Purchase #5 $213.91   5.243%   $225.1253   $225.13   $225.15   $225.10  
  Purchase #6 $134.32   11.389%   $149.6177   $149.62   $149.60   $149.60  
  Purchase #7 $184.65   10.799%   $204.5904   $204.59   $204.60   $204.60  
  7 purchase totals = $977.76       $1,068.5327   $1,068.54   $1,068.55   $1,068.50