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 $62.96   6.863%   $67.2809   $67.28   $67.30   $67.30  
  Purchase #2 $219.56   4.320%   $229.045   $229.05   $229.05   $229.00  
  Purchase #3 $156.91   8.213%   $169.797   $169.80   $169.80   $169.80  
  Purchase #4 $145.92   12.517%   $164.1848   $164.18   $164.20   $164.20  
  Purchase #5 $62.91   13.770%   $71.5727   $71.57   $71.55   $71.60  
  Purchase #6 $196.95   7.154%   $211.0398   $211.04   $211.05   $211.00  
  Purchase #7 $215.68   11.798%   $241.1259   $241.13   $241.15   $241.10  
  7 purchase totals = $1,060.89       $1,154.0461   $1,154.05   $1,154.10   $1,154.00