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 $148.68   5.608%   $157.018   $157.02   $157.00   $157.00  
  Purchase #2 $162.37   11.714%   $181.39   $181.39   $181.40   $181.40  
  Purchase #3 $82.75   11.697%   $92.4293   $92.43   $92.45   $92.40  
  Purchase #4 $220.37   6.665%   $235.0577   $235.06   $235.05   $235.10  
  Purchase #5 $117.93   13.163%   $133.4531   $133.45   $133.45   $133.50  
  Purchase #6 $181.98   12.659%   $205.0168   $205.02   $205.00   $205.00  
  Purchase #7 $155.72   5.117%   $163.6882   $163.69   $163.70   $163.70  
  7 purchase totals = $1,069.80       $1,168.0531   $1,168.06   $1,168.05   $1,168.10