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 $87.52   9.229%   $95.5972   $95.60   $95.60   $95.60  
  Purchase #2 $45.80   7.694%   $49.3239   $49.32   $49.30   $49.30  
  Purchase #3 $84.49   3.670%   $87.5908   $87.59   $87.60   $87.60  
  Purchase #4 $123.94   6.479%   $131.9701   $131.97   $131.95   $132.00  
  Purchase #5 $145.98   4.632%   $152.7418   $152.74   $152.75   $152.70  
  Purchase #6 $165.58   9.379%   $181.1097   $181.11   $181.10   $181.10  
  Purchase #7 $182.54   10.508%   $201.7213   $201.72   $201.70   $201.70  
  7 purchase totals = $835.85       $900.0548   $900.05   $900.00   $900.00