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 $197.82   7.774%   $213.1985   $213.20   $213.20   $213.20  
  Purchase #2 $53.43   4.168%   $55.657   $55.66   $55.65   $55.70  
  Purchase #3 $56.70   9.380%   $62.0185   $62.02   $62.00   $62.00  
  Purchase #4 $182.26   10.730%   $201.8165   $201.82   $201.80   $201.80  
  Purchase #5 $193.94   7.591%   $208.662   $208.66   $208.65   $208.70  
  Purchase #6 $130.50   4.107%   $135.8596   $135.86   $135.85   $135.90  
  Purchase #7 $166.47   11.399%   $185.4459   $185.45   $185.45   $185.40  
  7 purchase totals = $981.12       $1,062.6580   $1,062.67   $1,062.60   $1,062.70