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 $173.92   13.243%   $196.9522   $196.95   $196.95   $197.00  
  Purchase #2 $179.43   12.327%   $201.5483   $201.55   $201.55   $201.50  
  Purchase #3 $221.30   9.246%   $241.7614   $241.76   $241.75   $241.80  
  Purchase #4 $219.30   12.763%   $247.2893   $247.29   $247.30   $247.30  
  Purchase #5 $61.26   3.840%   $63.6124   $63.61   $63.60   $63.60  
  Purchase #6 $29.30   11.331%   $32.62   $32.62   $32.60   $32.60  
  Purchase #7 $47.35   5.123%   $49.7757   $49.78   $49.80   $49.80  
  7 purchase totals = $931.86       $1,033.5593   $1,033.56   $1,033.55   $1,033.60