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 $62.98   7.317%   $67.5882   $67.59   $67.60   $67.60  
  Purchase #2 $190.46   4.191%   $198.4422   $198.44   $198.45   $198.40  
  Purchase #3 $152.81   5.634%   $161.4193   $161.42   $161.40   $161.40  
  Purchase #4 $90.75   11.326%   $101.0283   $101.03   $101.05   $101.00  
  Purchase #5 $193.79   5.817%   $205.0628   $205.06   $205.05   $205.10  
  Purchase #6 $153.74   4.816%   $161.1441   $161.14   $161.15   $161.10  
  Purchase #7 $194.82   12.792%   $219.7414   $219.74   $219.75   $219.70  
  7 purchase totals = $1,039.35       $1,114.4263   $1,114.42   $1,114.45   $1,114.30