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 $69.29   7.671%   $74.6052   $74.61   $74.60   $74.60  
  Purchase #2 $24.91   4.841%   $26.1159   $26.12   $26.10   $26.10  
  Purchase #3 $209.84   11.544%   $234.0639   $234.06   $234.05   $234.10  
  Purchase #4 $172.89   13.193%   $195.6994   $195.70   $195.70   $195.70  
  Purchase #5 $165.97   7.609%   $178.5987   $178.60   $178.60   $178.60  
  Purchase #6 $20.56   9.845%   $22.5841   $22.58   $22.60   $22.60  
  Purchase #7 $144.60   7.209%   $155.0242   $155.02   $155.00   $155.00  
  7 purchase totals = $808.06       $886.6914   $886.69   $886.65   $886.70