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 $175.54   8.727%   $190.8594   $190.86   $190.85   $190.90  
  Purchase #2 $210.99   4.164%   $219.7756   $219.78   $219.80   $219.80  
  Purchase #3 $61.50   11.738%   $68.7189   $68.72   $68.70   $68.70  
  Purchase #4 $94.27   3.599%   $97.6628   $97.66   $97.65   $97.70  
  Purchase #5 $211.83   10.220%   $233.479   $233.48   $233.50   $233.50  
  Purchase #6 $62.60   5.421%   $65.9935   $65.99   $66.00   $66.00  
  Purchase #7 $172.71   10.330%   $190.5509   $190.55   $190.55   $190.60  
  7 purchase totals = $989.44       $1,067.0401   $1,067.04   $1,067.05   $1,067.20