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 $58.98   5.648%   $62.3112   $62.31   $62.30   $62.30  
  Purchase #2 $34.94   7.708%   $37.6332   $37.63   $37.65   $37.60  
  Purchase #3 $207.52   6.603%   $221.2225   $221.22   $221.20   $221.20  
  Purchase #4 $128.55   12.385%   $144.4709   $144.47   $144.45   $144.50  
  Purchase #5 $191.67   9.477%   $209.8346   $209.83   $209.85   $209.80  
  Purchase #6 $183.90   9.290%   $200.9843   $200.98   $201.00   $201.00  
  Purchase #7 $180.90   11.794%   $202.2353   $202.24   $202.25   $202.20  
  7 purchase totals = $986.46       $1,078.6920   $1,078.68   $1,078.70   $1,078.60