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 $98.92   6.113%   $104.967   $104.97   $104.95   $105.00  
  Purchase #2 $156.56   11.803%   $175.0388   $175.04   $175.05   $175.00  
  Purchase #3 $201.93   7.628%   $217.3332   $217.33   $217.35   $217.30  
  Purchase #4 $117.75   10.294%   $129.8712   $129.87   $129.85   $129.90  
  Purchase #5 $231.90   11.416%   $258.3737   $258.37   $258.35   $258.40  
  Purchase #6 $156.93   3.313%   $162.1291   $162.13   $162.15   $162.10  
  Purchase #7 $11.64   11.173%   $12.9405   $12.94   $12.95   $12.90  
  7 purchase totals = $975.63       $1,060.6535   $1,060.65   $1,060.65   $1,060.60