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 $226.92   8.220%   $245.5728   $245.57   $245.55   $245.60  
  Purchase #2 $220.83   4.826%   $231.4873   $231.49   $231.50   $231.50  
  Purchase #3 $31.89   7.280%   $34.2116   $34.21   $34.20   $34.20  
  Purchase #4 $114.80   5.278%   $120.8591   $120.86   $120.85   $120.90  
  Purchase #5 $195.53   7.364%   $209.9288   $209.93   $209.95   $209.90  
  Purchase #6 $52.85   4.852%   $55.4143   $55.41   $55.40   $55.40  
  Purchase #7 $111.58   4.676%   $116.7975   $116.80   $116.80   $116.80  
  7 purchase totals = $954.40       $1,014.2714   $1,014.27   $1,014.25   $1,014.30