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 $84.35   11.867%   $94.3598   $94.36   $94.35   $94.40  
  Purchase #2 $129.51   5.837%   $137.0695   $137.07   $137.05   $137.10  
  Purchase #3 $45.55   12.482%   $51.2356   $51.24   $51.25   $51.20  
  Purchase #4 $223.67   12.428%   $251.4677   $251.47   $251.45   $251.50  
  Purchase #5 $82.76   6.474%   $88.1179   $88.12   $88.10   $88.10  
  Purchase #6 $160.32   3.406%   $165.7805   $165.78   $165.80   $165.80  
  Purchase #7 $222.85   6.626%   $237.616   $237.62   $237.60   $237.60  
  7 purchase totals = $949.01       $1,025.6470   $1,025.66   $1,025.60   $1,025.70