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 $72.39   4.858%   $75.9067   $75.91   $75.90   $75.90  
  Purchase #2 $101.50   3.495%   $105.0474   $105.05   $105.05   $105.00  
  Purchase #3 $129.93   4.737%   $136.0848   $136.08   $136.10   $136.10  
  Purchase #4 $60.26   3.378%   $62.2956   $62.30   $62.30   $62.30  
  Purchase #5 $60.47   4.641%   $63.2764   $63.28   $63.30   $63.30  
  Purchase #6 $223.48   4.210%   $232.8885   $232.89   $232.90   $232.90  
  Purchase #7 $25.47   4.731%   $26.675   $26.68   $26.70   $26.70  
  7 purchase totals = $673.50       $702.1744   $702.19   $702.25   $702.20