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 $216.66   5.116%   $227.7443   $227.74   $227.75   $227.70  
  Purchase #2 $53.59   12.602%   $60.3434   $60.34   $60.35   $60.30  
  Purchase #3 $203.55   7.736%   $219.2966   $219.30   $219.30   $219.30  
  Purchase #4 $117.40   4.638%   $122.845   $122.85   $122.85   $122.80  
  Purchase #5 $133.69   11.277%   $148.7662   $148.77   $148.75   $148.80  
  Purchase #6 $174.66   5.556%   $184.3641   $184.36   $184.35   $184.40  
  Purchase #7 $97.79   4.526%   $102.216   $102.22   $102.20   $102.20  
  7 purchase totals = $997.34       $1,065.5756   $1,065.58   $1,065.55   $1,065.50