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 $162.51   7.567%   $174.8071   $174.81   $174.80   $174.80  
  Purchase #2 $53.79   13.363%   $60.978   $60.98   $61.00   $61.00  
  Purchase #3 $42.67   6.571%   $45.4738   $45.47   $45.45   $45.50  
  Purchase #4 $80.29   5.315%   $84.5574   $84.56   $84.55   $84.60  
  Purchase #5 $241.55   7.277%   $259.1276   $259.13   $259.15   $259.10  
  Purchase #6 $233.42   10.829%   $258.6971   $258.70   $258.70   $258.70  
  Purchase #7 $215.81   8.675%   $234.5315   $234.53   $234.55   $234.50  
  7 purchase totals = $1,030.04       $1,118.1725   $1,118.18   $1,118.20   $1,118.20