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 $111.30   4.533%   $116.3452   $116.35   $116.35   $116.30  
  Purchase #2 $228.49   6.424%   $243.1682   $243.17   $243.15   $243.20  
  Purchase #3 $169.45   4.571%   $177.1956   $177.20   $177.20   $177.20  
  Purchase #4 $87.86   5.148%   $92.383   $92.38   $92.40   $92.40  
  Purchase #5 $59.94   6.689%   $63.9494   $63.95   $63.95   $63.90  
  Purchase #6 $239.28   12.803%   $269.915   $269.92   $269.90   $269.90  
  Purchase #7 $136.50   11.374%   $152.0255   $152.03   $152.05   $152.00  
  7 purchase totals = $1,032.82       $1,114.9819   $1,115.00   $1,115.00   $1,114.90