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 $181.48   9.136%   $198.06   $198.06   $198.05   $198.10  
  Purchase #2 $59.28   13.598%   $67.3409   $67.34   $67.35   $67.30  
  Purchase #3 $218.89   12.543%   $246.3454   $246.35   $246.35   $246.30  
  Purchase #4 $24.77   7.373%   $26.5963   $26.60   $26.60   $26.60  
  Purchase #5 $234.85   13.668%   $266.9493   $266.95   $266.95   $266.90  
  Purchase #6 $193.32   13.243%   $218.9214   $218.92   $218.90   $218.90  
  Purchase #7 $7.79   3.222%   $8.041   $8.04   $8.05   $8.00  
  7 purchase totals = $920.38       $1,032.2543   $1,032.26   $1,032.25   $1,032.10