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 $41.69   10.797%   $46.1913   $46.19   $46.20   $46.20  
  Purchase #2 $151.74   5.475%   $160.0478   $160.05   $160.05   $160.00  
  Purchase #3 $167.35   5.504%   $176.5609   $176.56   $176.55   $176.60  
  Purchase #4 $188.63   4.286%   $196.7147   $196.71   $196.70   $196.70  
  Purchase #5 $187.92   9.150%   $205.1147   $205.11   $205.10   $205.10  
  Purchase #6 $238.58   5.807%   $252.4343   $252.43   $252.45   $252.40  
  Purchase #7 $245.54   5.410%   $258.8237   $258.82   $258.80   $258.80  
  7 purchase totals = $1,221.45       $1,295.8874   $1,295.87   $1,295.85   $1,295.80