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 $152.67   11.145%   $169.6851   $169.69   $169.70   $169.70  
  Purchase #2 $216.79   3.197%   $223.7208   $223.72   $223.70   $223.70  
  Purchase #3 $20.62   12.239%   $23.1437   $23.14   $23.15   $23.10  
  Purchase #4 $125.41   12.162%   $140.6624   $140.66   $140.65   $140.70  
  Purchase #5 $211.93   11.215%   $235.6979   $235.70   $235.70   $235.70  
  Purchase #6 $66.43   13.184%   $75.1881   $75.19   $75.20   $75.20  
  Purchase #7 $158.66   11.670%   $177.1756   $177.18   $177.20   $177.20  
  7 purchase totals = $952.51       $1,045.2736   $1,045.28   $1,045.30   $1,045.30