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 $182.52   4.516%   $190.7626   $190.76   $190.75   $190.80  
  Purchase #2 $193.34   8.421%   $209.6212   $209.62   $209.60   $209.60  
  Purchase #3 $219.83   4.637%   $230.0235   $230.02   $230.00   $230.00  
  Purchase #4 $233.72   6.642%   $249.2437   $249.24   $249.25   $249.20  
  Purchase #5 $149.57   8.572%   $162.3911   $162.39   $162.40   $162.40  
  Purchase #6 $164.49   11.474%   $183.3636   $183.36   $183.35   $183.40  
  Purchase #7 $22.64   8.233%   $24.504   $24.50   $24.50   $24.50  
  7 purchase totals = $1,166.11       $1,249.9097   $1,249.89   $1,249.85   $1,249.90