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 $176.31   10.608%   $195.013   $195.01   $195.00   $195.00  
  Purchase #2 $60.89   8.261%   $65.9201   $65.92   $65.90   $65.90  
  Purchase #3 $176.93   4.452%   $184.8069   $184.81   $184.80   $184.80  
  Purchase #4 $60.25   11.557%   $67.2131   $67.21   $67.20   $67.20  
  Purchase #5 $134.87   6.709%   $143.9184   $143.92   $143.90   $143.90  
  Purchase #6 $33.88   7.318%   $36.3593   $36.36   $36.35   $36.40  
  Purchase #7 $75.59   10.185%   $83.2888   $83.29   $83.30   $83.30  
  7 purchase totals = $718.72       $776.5196   $776.52   $776.45   $776.50