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 $59.69   8.249%   $64.6138   $64.61   $64.60   $64.60  
  Purchase #2 $6.75   8.656%   $7.3343   $7.33   $7.35   $7.30  
  Purchase #3 $81.92   7.162%   $87.7871   $87.79   $87.80   $87.80  
  Purchase #4 $86.35   10.577%   $95.4832   $95.48   $95.50   $95.50  
  Purchase #5 $95.83   11.257%   $106.6176   $106.62   $106.60   $106.60  
  Purchase #6 $7.35   8.424%   $7.9692   $7.97   $7.95   $8.00  
  Purchase #7 $36.36   13.258%   $41.1806   $41.18   $41.20   $41.20  
  7 purchase totals = $374.25       $410.9858   $410.98   $411.00   $411.00