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 $60.81   10.144%   $66.9786   $66.98   $67.00   $67.00  
  Purchase #2 $191.25   10.330%   $211.0061   $211.01   $211.00   $211.00  
  Purchase #3 $20.97   11.543%   $23.3906   $23.39   $23.40   $23.40  
  Purchase #4 $208.78   7.151%   $223.7099   $223.71   $223.70   $223.70  
  Purchase #5 $25.56   7.874%   $27.5726   $27.57   $27.55   $27.60  
  Purchase #6 $238.37   3.475%   $246.6534   $246.65   $246.65   $246.70  
  Purchase #7 $245.83   6.627%   $262.1212   $262.12   $262.10   $262.10  
  7 purchase totals = $991.57       $1,061.4324   $1,061.43   $1,061.40   $1,061.50