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 $182.69   5.783%   $193.255   $193.26   $193.25   $193.30  
  Purchase #2 $92.39   7.543%   $99.359   $99.36   $99.35   $99.40  
  Purchase #3 $41.93   8.797%   $45.6186   $45.62   $45.60   $45.60  
  Purchase #4 $208.58   5.759%   $220.5921   $220.59   $220.60   $220.60  
  Purchase #5 $138.54   10.639%   $153.2793   $153.28   $153.30   $153.30  
  Purchase #6 $159.70   8.215%   $172.8194   $172.82   $172.80   $172.80  
  Purchase #7 $189.76   7.188%   $203.3999   $203.40   $203.40   $203.40  
  7 purchase totals = $1,013.59       $1,088.3233   $1,088.33   $1,088.30   $1,088.40