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 $68.72   11.426%   $76.5719   $76.57   $76.55   $76.60  
  Purchase #2 $230.90   10.214%   $254.4841   $254.48   $254.50   $254.50  
  Purchase #3 $246.95   12.151%   $276.9569   $276.96   $276.95   $277.00  
  Purchase #4 $86.88   9.306%   $94.9651   $94.97   $94.95   $95.00  
  Purchase #5 $192.57   5.134%   $202.4565   $202.46   $202.45   $202.50  
  Purchase #6 $157.85   12.350%   $177.3445   $177.34   $177.35   $177.30  
  Purchase #7 $206.31   5.853%   $218.3853   $218.39   $218.40   $218.40  
  7 purchase totals = $1,190.18       $1,301.1643   $1,301.17   $1,301.15   $1,301.30