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 $60.95   11.419%   $67.9099   $67.91   $67.90   $67.90  
  Purchase #2 $187.66   9.106%   $204.7483   $204.75   $204.75   $204.70  
  Purchase #3 $244.61   5.487%   $258.0318   $258.03   $258.05   $258.00  
  Purchase #4 $172.46   8.156%   $186.5258   $186.53   $186.55   $186.50  
  Purchase #5 $184.74   6.808%   $197.3171   $197.32   $197.30   $197.30  
  Purchase #6 $126.32   12.216%   $141.7513   $141.75   $141.75   $141.80  
  Purchase #7 $191.95   5.289%   $202.1022   $202.10   $202.10   $202.10  
  7 purchase totals = $1,168.69       $1,258.3864   $1,258.39   $1,258.40   $1,258.30