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 $68.61   11.170%   $76.2737   $76.27   $76.25   $76.30  
  Purchase #2 $214.31   9.372%   $234.3951   $234.40   $234.40   $234.40  
  Purchase #3 $230.56   9.141%   $251.6355   $251.64   $251.65   $251.60  
  Purchase #4 $226.84   3.534%   $234.8565   $234.86   $234.85   $234.90  
  Purchase #5 $59.37   4.278%   $61.9098   $61.91   $61.90   $61.90  
  Purchase #6 $231.80   11.562%   $258.6007   $258.60   $258.60   $258.60  
  Purchase #7 $29.61   6.209%   $31.4485   $31.45   $31.45   $31.40  
  7 purchase totals = $1,061.10       $1,149.1198   $1,149.13   $1,149.10   $1,149.10