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 $87.88   10.239%   $96.878   $96.88   $96.90   $96.90  
  Purchase #2 $201.41   7.372%   $216.2579   $216.26   $216.25   $216.30  
  Purchase #3 $215.38   13.141%   $243.6831   $243.68   $243.70   $243.70  
  Purchase #4 $237.47   13.360%   $269.196   $269.20   $269.20   $269.20  
  Purchase #5 $87.90   12.626%   $98.9983   $99.00   $99.00   $99.00  
  Purchase #6 $133.97   3.836%   $139.1091   $139.11   $139.10   $139.10  
  Purchase #7 $72.31   11.532%   $80.6488   $80.65   $80.65   $80.60  
  7 purchase totals = $1,036.32       $1,144.7712   $1,144.78   $1,144.80   $1,144.80