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 $58.71   7.218%   $62.9477   $62.95   $62.95   $62.90  
  Purchase #2 $199.48   11.467%   $222.3544   $222.35   $222.35   $222.40  
  Purchase #3 $248.54   8.315%   $269.2061   $269.21   $269.20   $269.20  
  Purchase #4 $54.79   5.627%   $57.873   $57.87   $57.85   $57.90  
  Purchase #5 $86.76   5.815%   $91.8051   $91.81   $91.80   $91.80  
  Purchase #6 $184.85   7.673%   $199.0335   $199.03   $199.05   $199.00  
  Purchase #7 $194.37   9.870%   $213.5543   $213.55   $213.55   $213.60  
  7 purchase totals = $1,027.50       $1,116.7741   $1,116.77   $1,116.75   $1,116.80