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 $176.59   3.249%   $182.3274   $182.33   $182.35   $182.30  
  Purchase #2 $39.77   11.749%   $44.4426   $44.44   $44.45   $44.40  
  Purchase #3 $216.76   12.328%   $243.4822   $243.48   $243.50   $243.50  
  Purchase #4 $220.91   3.774%   $229.2471   $229.25   $229.25   $229.20  
  Purchase #5 $57.56   12.311%   $64.6462   $64.65   $64.65   $64.60  
  Purchase #6 $233.67   7.613%   $251.4593   $251.46   $251.45   $251.50  
  Purchase #7 $27.96   5.749%   $29.5674   $29.57   $29.55   $29.60  
  7 purchase totals = $973.22       $1,045.1722   $1,045.18   $1,045.20   $1,045.10