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 $117.99   6.450%   $125.6004   $125.60   $125.60   $125.60  
  Purchase #2 $173.66   13.630%   $197.3299   $197.33   $197.35   $197.30  
  Purchase #3 $96.70   8.481%   $104.9011   $104.90   $104.90   $104.90  
  Purchase #4 $155.86   5.103%   $163.8135   $163.81   $163.80   $163.80  
  Purchase #5 $184.55   10.507%   $203.9407   $203.94   $203.95   $203.90  
  Purchase #6 $174.59   5.842%   $184.7895   $184.79   $184.80   $184.80  
  Purchase #7 $32.90   4.235%   $34.2933   $34.29   $34.30   $34.30  
  7 purchase totals = $936.25       $1,014.6684   $1,014.66   $1,014.70   $1,014.60