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 $23.47   10.511%   $25.9369   $25.94   $25.95   $25.90  
  Purchase #2 $146.48   10.295%   $161.5601   $161.56   $161.55   $161.60  
  Purchase #3 $201.99   8.429%   $219.0157   $219.02   $219.00   $219.00  
  Purchase #4 $134.35   12.734%   $151.4581   $151.46   $151.45   $151.50  
  Purchase #5 $226.34   10.582%   $250.2913   $250.29   $250.30   $250.30  
  Purchase #6 $113.28   4.651%   $118.5487   $118.55   $118.55   $118.50  
  Purchase #7 $173.35   10.609%   $191.7407   $191.74   $191.75   $191.70  
  7 purchase totals = $1,019.26       $1,118.5515   $1,118.56   $1,118.55   $1,118.50