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 $104.98   10.690%   $116.2024   $116.20   $116.20   $116.20  
  Purchase #2 $163.87   5.183%   $172.3634   $172.36   $172.35   $172.40  
  Purchase #3 $215.61   5.716%   $227.9343   $227.93   $227.95   $227.90  
  Purchase #4 $246.47   4.688%   $258.0245   $258.02   $258.00   $258.00  
  Purchase #5 $21.84   10.746%   $24.1869   $24.19   $24.20   $24.20  
  Purchase #6 $10.49   10.329%   $11.5735   $11.57   $11.55   $11.60  
  Purchase #7 $210.89   10.585%   $233.2127   $233.21   $233.20   $233.20  
  7 purchase totals = $974.15       $1,043.4977   $1,043.48   $1,043.45   $1,043.50