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 $44.94   3.369%   $46.454   $46.45   $46.45   $46.50  
  Purchase #2 $197.57   13.446%   $224.1353   $224.14   $224.15   $224.10  
  Purchase #3 $155.54   7.356%   $166.9815   $166.98   $167.00   $167.00  
  Purchase #4 $210.28   9.855%   $231.0031   $231.00   $231.00   $231.00  
  Purchase #5 $23.48   13.495%   $26.6486   $26.65   $26.65   $26.60  
  Purchase #6 $215.75   9.459%   $236.1578   $236.16   $236.15   $236.20  
  Purchase #7 $41.96   4.233%   $43.7362   $43.74   $43.75   $43.70  
  7 purchase totals = $889.52       $975.1165   $975.12   $975.15   $975.10