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 $82.74   13.640%   $94.0257   $94.03   $94.05   $94.00  
  Purchase #2 $214.93   7.321%   $230.665   $230.67   $230.65   $230.70  
  Purchase #3 $89.62   6.489%   $95.4354   $95.44   $95.45   $95.40  
  Purchase #4 $104.97   8.162%   $113.5377   $113.54   $113.55   $113.50  
  Purchase #5 $225.72   11.203%   $251.0074   $251.01   $251.00   $251.00  
  Purchase #6 $42.57   12.748%   $47.9968   $48.00   $48.00   $48.00  
  Purchase #7 $102.74   7.264%   $110.203   $110.20   $110.20   $110.20  
  7 purchase totals = $863.29       $942.8710   $942.89   $942.90   $942.80