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 $96.61   9.786%   $106.0643   $106.06   $106.05   $106.10  
  Purchase #2 $95.28   11.206%   $105.9571   $105.96   $105.95   $106.00  
  Purchase #3 $184.52   4.285%   $192.4267   $192.43   $192.45   $192.40  
  Purchase #4 $191.52   4.419%   $199.9833   $199.98   $200.00   $200.00  
  Purchase #5 $167.49   3.289%   $172.9987   $173.00   $173.00   $173.00  
  Purchase #6 $156.87   11.354%   $174.681   $174.68   $174.70   $174.70  
  Purchase #7 $8.98   12.590%   $10.1106   $10.11   $10.10   $10.10  
  7 purchase totals = $901.27       $962.2217   $962.22   $962.25   $962.30