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 $24.32   7.201%   $26.0713   $26.07   $26.05   $26.10  
  Purchase #2 $245.73   9.609%   $269.3422   $269.34   $269.35   $269.30  
  Purchase #3 $116.32   3.612%   $120.5215   $120.52   $120.50   $120.50  
  Purchase #4 $11.42   5.564%   $12.0554   $12.06   $12.05   $12.10  
  Purchase #5 $174.79   10.470%   $193.0905   $193.09   $193.10   $193.10  
  Purchase #6 $23.43   9.679%   $25.6978   $25.70   $25.70   $25.70  
  Purchase #7 $116.57   4.320%   $121.6058   $121.61   $121.60   $121.60  
  7 purchase totals = $712.58       $768.3845   $768.39   $768.35   $768.40