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 $194.51   3.271%   $200.8724   $200.87   $200.85   $200.90  
  Purchase #2 $23.84   9.351%   $26.0693   $26.07   $26.05   $26.10  
  Purchase #3 $236.26   3.136%   $243.6691   $243.67   $243.65   $243.70  
  Purchase #4 $183.94   10.308%   $202.9005   $202.90   $202.90   $202.90  
  Purchase #5 $177.61   6.502%   $189.1582   $189.16   $189.15   $189.20  
  Purchase #6 $91.41   4.367%   $95.4019   $95.40   $95.40   $95.40  
  Purchase #7 $235.67   3.127%   $243.0394   $243.04   $243.05   $243.00  
  7 purchase totals = $1,143.24       $1,201.1108   $1,201.11   $1,201.05   $1,201.20