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 $178.36   9.335%   $195.0099   $195.01   $195.00   $195.00  
  Purchase #2 $236.34   4.261%   $246.4104   $246.41   $246.40   $246.40  
  Purchase #3 $183.62   7.729%   $197.812   $197.81   $197.80   $197.80  
  Purchase #4 $79.74   3.166%   $82.2646   $82.26   $82.25   $82.30  
  Purchase #5 $118.84   5.697%   $125.6103   $125.61   $125.60   $125.60  
  Purchase #6 $179.33   6.321%   $190.6654   $190.67   $190.65   $190.70  
  Purchase #7 $68.62   13.375%   $77.7979   $77.80   $77.80   $77.80  
  7 purchase totals = $1,044.85       $1,115.5705   $1,115.57   $1,115.50   $1,115.60