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 $63.51   9.864%   $69.7746   $69.77   $69.75   $69.80  
  Purchase #2 $242.94   4.801%   $254.6035   $254.60   $254.60   $254.60  
  Purchase #3 $237.49   3.870%   $246.6809   $246.68   $246.70   $246.70  
  Purchase #4 $110.49   6.409%   $117.5713   $117.57   $117.55   $117.60  
  Purchase #5 $23.43   11.455%   $26.1139   $26.11   $26.10   $26.10  
  Purchase #6 $215.38   6.361%   $229.0803   $229.08   $229.10   $229.10  
  Purchase #7 $199.30   3.413%   $206.1021   $206.10   $206.10   $206.10  
  7 purchase totals = $1,092.54       $1,149.9266   $1,149.91   $1,149.90   $1,150.00