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 $54.93   9.225%   $59.9973   $60.00   $60.00   $60.00  
  Purchase #2 $218.35   8.345%   $236.5713   $236.57   $236.55   $236.60  
  Purchase #3 $37.67   11.423%   $41.973   $41.97   $41.95   $42.00  
  Purchase #4 $230.73   7.435%   $247.8848   $247.88   $247.90   $247.90  
  Purchase #5 $6.98   6.206%   $7.4132   $7.41   $7.40   $7.40  
  Purchase #6 $190.86   12.285%   $214.3072   $214.31   $214.30   $214.30  
  Purchase #7 $229.75   6.256%   $244.1232   $244.12   $244.10   $244.10  
  7 purchase totals = $969.27       $1,052.2700   $1,052.26   $1,052.20   $1,052.30