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 $41.31   5.675%   $43.6543   $43.65   $43.65   $43.70  
  Purchase #2 $237.46   3.424%   $245.5906   $245.59   $245.60   $245.60  
  Purchase #3 $87.70   9.410%   $95.9526   $95.95   $95.95   $96.00  
  Purchase #4 $64.78   6.450%   $68.9583   $68.96   $68.95   $69.00  
  Purchase #5 $26.32   4.137%   $27.4089   $27.41   $27.40   $27.40  
  Purchase #6 $84.90   10.853%   $94.1142   $94.11   $94.10   $94.10  
  Purchase #7 $237.46   3.409%   $245.555   $245.56   $245.55   $245.60  
  7 purchase totals = $779.93       $821.2339   $821.23   $821.20   $821.40