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 $191.78   7.767%   $206.6756   $206.68   $206.70   $206.70  
  Purchase #2 $84.55   13.131%   $95.6523   $95.65   $95.65   $95.70  
  Purchase #3 $191.62   4.785%   $200.789   $200.79   $200.80   $200.80  
  Purchase #4 $142.38   11.560%   $158.8391   $158.84   $158.85   $158.80  
  Purchase #5 $147.76   11.470%   $164.7081   $164.71   $164.70   $164.70  
  Purchase #6 $180.38   4.567%   $188.618   $188.62   $188.60   $188.60  
  Purchase #7 $189.85   11.331%   $211.3619   $211.36   $211.35   $211.40  
  7 purchase totals = $1,128.32       $1,226.6440   $1,226.65   $1,226.65   $1,226.70