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 $164.64   5.227%   $173.2457   $173.25   $173.25   $173.20  
  Purchase #2 $94.84   11.748%   $105.9818   $105.98   $106.00   $106.00  
  Purchase #3 $173.63   6.294%   $184.5583   $184.56   $184.55   $184.60  
  Purchase #4 $109.71   12.681%   $123.6223   $123.62   $123.60   $123.60  
  Purchase #5 $229.58   7.434%   $246.647   $246.65   $246.65   $246.60  
  Purchase #6 $126.86   7.276%   $136.0903   $136.09   $136.10   $136.10  
  Purchase #7 $86.75   6.631%   $92.5024   $92.50   $92.50   $92.50  
  7 purchase totals = $986.01       $1,062.6478   $1,062.65   $1,062.65   $1,062.60