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 $108.39   5.212%   $114.0393   $114.04   $114.05   $114.00  
  Purchase #2 $174.79   9.192%   $190.8567   $190.86   $190.85   $190.90  
  Purchase #3 $120.83   12.562%   $136.0087   $136.01   $136.00   $136.00  
  Purchase #4 $80.26   4.796%   $84.1093   $84.11   $84.10   $84.10  
  Purchase #5 $203.95   4.434%   $212.9931   $212.99   $213.00   $213.00  
  Purchase #6 $127.86   10.510%   $141.2981   $141.30   $141.30   $141.30  
  Purchase #7 $207.78   5.171%   $218.5243   $218.52   $218.50   $218.50  
  7 purchase totals = $1,023.86       $1,097.8295   $1,097.83   $1,097.80   $1,097.80