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 $175.43   12.464%   $197.2956   $197.30   $197.30   $197.30  
  Purchase #2 $164.54   11.524%   $183.5016   $183.50   $183.50   $183.50  
  Purchase #3 $94.69   11.716%   $105.7839   $105.78   $105.80   $105.80  
  Purchase #4 $211.51   3.794%   $219.5347   $219.53   $219.55   $219.50  
  Purchase #5 $11.45   8.594%   $12.434   $12.43   $12.45   $12.40  
  Purchase #6 $201.26   13.616%   $228.6636   $228.66   $228.65   $228.70  
  Purchase #7 $116.64   3.140%   $120.3025   $120.30   $120.30   $120.30  
  7 purchase totals = $975.52       $1,067.5159   $1,067.50   $1,067.55   $1,067.50