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 $177.35   10.343%   $195.6933   $195.69   $195.70   $195.70  
  Purchase #2 $148.97   11.807%   $166.5589   $166.56   $166.55   $166.60  
  Purchase #3 $29.71   10.377%   $32.793   $32.79   $32.80   $32.80  
  Purchase #4 $240.87   4.562%   $251.8585   $251.86   $251.85   $251.90  
  Purchase #5 $178.42   7.393%   $191.6106   $191.61   $191.60   $191.60  
  Purchase #6 $99.33   5.773%   $105.0643   $105.06   $105.05   $105.10  
  Purchase #7 $240.77   4.790%   $252.3029   $252.30   $252.30   $252.30  
  7 purchase totals = $1,115.42       $1,195.8815   $1,195.87   $1,195.85   $1,196.00