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 $213.93   10.813%   $237.0623   $237.06   $237.05   $237.10  
  Purchase #2 $241.83   12.593%   $272.2837   $272.28   $272.30   $272.30  
  Purchase #3 $51.55   10.283%   $56.8509   $56.85   $56.85   $56.90  
  Purchase #4 $246.30   3.427%   $254.7407   $254.74   $254.75   $254.70  
  Purchase #5 $29.35   9.776%   $32.2193   $32.22   $32.20   $32.20  
  Purchase #6 $156.64   5.511%   $165.2724   $165.27   $165.25   $165.30  
  Purchase #7 $171.67   6.709%   $183.1873   $183.19   $183.20   $183.20  
  7 purchase totals = $1,111.27       $1,201.6166   $1,201.61   $1,201.60   $1,201.70