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 $219.43   4.385%   $229.052   $229.05   $229.05   $229.10  
  Purchase #2 $128.98   7.282%   $138.3723   $138.37   $138.35   $138.40  
  Purchase #3 $67.38   4.364%   $70.3205   $70.32   $70.30   $70.30  
  Purchase #4 $207.67   6.501%   $221.1706   $221.17   $221.15   $221.20  
  Purchase #5 $232.67   6.210%   $247.1188   $247.12   $247.10   $247.10  
  Purchase #6 $9.47   5.667%   $10.0067   $10.01   $10.00   $10.00  
  Purchase #7 $122.25   12.212%   $137.1792   $137.18   $137.20   $137.20  
  7 purchase totals = $987.85       $1,053.2201   $1,053.22   $1,053.15   $1,053.30