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 $166.31   5.808%   $175.9693   $175.97   $175.95   $176.00  
  Purchase #2 $88.67   8.193%   $95.9347   $95.93   $95.95   $95.90  
  Purchase #3 $5.75   10.537%   $6.3559   $6.36   $6.35   $6.40  
  Purchase #4 $163.78   4.153%   $170.5818   $170.58   $170.60   $170.60  
  Purchase #5 $163.87   10.656%   $181.332   $181.33   $181.35   $181.30  
  Purchase #6 $216.43   7.495%   $232.6514   $232.65   $232.65   $232.70  
  Purchase #7 $151.48   11.517%   $168.926   $168.93   $168.95   $168.90  
  7 purchase totals = $956.29       $1,031.7511   $1,031.75   $1,031.80   $1,031.80