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 $69.83   8.405%   $75.6992   $75.70   $75.70   $75.70  
  Purchase #2 $176.65   3.537%   $182.8981   $182.90   $182.90   $182.90  
  Purchase #3 $183.50   9.507%   $200.9453   $200.95   $200.95   $200.90  
  Purchase #4 $242.82   6.518%   $258.647   $258.65   $258.65   $258.60  
  Purchase #5 $150.33   13.609%   $170.7884   $170.79   $170.80   $170.80  
  Purchase #6 $12.44   9.874%   $13.6683   $13.67   $13.65   $13.70  
  Purchase #7 $184.99   8.643%   $200.9787   $200.98   $201.00   $201.00  
  7 purchase totals = $1,020.56       $1,103.6250   $1,103.64   $1,103.65   $1,103.60