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 $93.33   3.401%   $96.5042   $96.50   $96.50   $96.50  
  Purchase #2 $136.79   4.573%   $143.0454   $143.05   $143.05   $143.00  
  Purchase #3 $66.69   5.519%   $70.3706   $70.37   $70.35   $70.40  
  Purchase #4 $220.30   6.586%   $234.809   $234.81   $234.80   $234.80  
  Purchase #5 $237.82   11.289%   $264.6675   $264.67   $264.65   $264.70  
  Purchase #6 $20.26   3.277%   $20.9239   $20.92   $20.90   $20.90  
  Purchase #7 $191.57   5.407%   $201.9282   $201.93   $201.95   $201.90  
  7 purchase totals = $966.76       $1,032.2488   $1,032.25   $1,032.20   $1,032.20