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 $231.97   8.520%   $251.7338   $251.73   $251.75   $251.70  
  Purchase #2 $197.96   6.676%   $211.1758   $211.18   $211.20   $211.20  
  Purchase #3 $196.81   5.661%   $207.9514   $207.95   $207.95   $208.00  
  Purchase #4 $155.99   13.540%   $177.111   $177.11   $177.10   $177.10  
  Purchase #5 $181.78   11.348%   $202.4084   $202.41   $202.40   $202.40  
  Purchase #6 $199.98   7.650%   $215.2785   $215.28   $215.30   $215.30  
  Purchase #7 $172.84   13.317%   $195.8571   $195.86   $195.85   $195.90  
  7 purchase totals = $1,337.33       $1,461.5160   $1,461.52   $1,461.55   $1,461.60