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 $43.34   6.765%   $46.272   $46.27   $46.25   $46.30  
  Purchase #2 $188.67   12.134%   $211.5632   $211.56   $211.55   $211.60  
  Purchase #3 $62.94   5.494%   $66.3979   $66.40   $66.40   $66.40  
  Purchase #4 $69.26   8.564%   $75.1914   $75.19   $75.20   $75.20  
  Purchase #5 $162.42   11.678%   $181.3874   $181.39   $181.40   $181.40  
  Purchase #6 $59.85   11.157%   $66.5275   $66.53   $66.55   $66.50  
  Purchase #7 $45.65   4.421%   $47.6682   $47.67   $47.65   $47.70  
  7 purchase totals = $632.13       $695.0076   $695.01   $695.00   $695.10