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 $68.28   9.336%   $74.6546   $74.65   $74.65   $74.70  
  Purchase #2 $26.67   10.616%   $29.5013   $29.50   $29.50   $29.50  
  Purchase #3 $58.79   9.734%   $64.5126   $64.51   $64.50   $64.50  
  Purchase #4 $60.85   12.470%   $68.438   $68.44   $68.45   $68.40  
  Purchase #5 $131.58   3.239%   $135.8419   $135.84   $135.85   $135.80  
  Purchase #6 $168.32   5.858%   $178.1802   $178.18   $178.20   $178.20  
  Purchase #7 $184.62   3.144%   $190.4245   $190.42   $190.40   $190.40  
  7 purchase totals = $699.11       $741.5531   $741.54   $741.55   $741.50