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 $195.64   8.418%   $212.109   $212.11   $212.10   $212.10  
  Purchase #2 $186.95   10.702%   $206.9574   $206.96   $206.95   $207.00  
  Purchase #3 $31.54   8.732%   $34.2941   $34.29   $34.30   $34.30  
  Purchase #4 $32.36   8.199%   $35.0132   $35.01   $35.00   $35.00  
  Purchase #5 $164.28   13.539%   $186.5219   $186.52   $186.50   $186.50  
  Purchase #6 $195.95   6.575%   $208.8337   $208.83   $208.85   $208.80  
  Purchase #7 $143.67   11.783%   $160.5986   $160.60   $160.60   $160.60  
  7 purchase totals = $950.39       $1,044.3279   $1,044.32   $1,044.30   $1,044.30