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 $211.70   9.400%   $231.5998   $231.60   $231.60   $231.60  
  Purchase #2 $95.30   7.733%   $102.6695   $102.67   $102.65   $102.70  
  Purchase #3 $151.60   11.337%   $168.7869   $168.79   $168.80   $168.80  
  Purchase #4 $64.32   3.858%   $66.8015   $66.80   $66.80   $66.80  
  Purchase #5 $169.49   10.387%   $187.0949   $187.09   $187.10   $187.10  
  Purchase #6 $128.58   5.313%   $135.4115   $135.41   $135.40   $135.40  
  Purchase #7 $206.35   5.795%   $218.308   $218.31   $218.30   $218.30  
  7 purchase totals = $1,027.34       $1,110.6721   $1,110.67   $1,110.65   $1,110.70