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 $163.41   6.849%   $174.602   $174.60   $174.60   $174.60  
  Purchase #2 $54.97   8.350%   $59.56   $59.56   $59.55   $59.60  
  Purchase #3 $218.88   3.158%   $225.7922   $225.79   $225.80   $225.80  
  Purchase #4 $148.70   12.521%   $167.3187   $167.32   $167.30   $167.30  
  Purchase #5 $62.51   3.577%   $64.746   $64.75   $64.75   $64.70  
  Purchase #6 $202.99   8.213%   $219.6616   $219.66   $219.65   $219.70  
  Purchase #7 $27.87   8.760%   $30.3114   $30.31   $30.30   $30.30  
  7 purchase totals = $879.33       $941.9919   $941.99   $941.95   $942.00