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 $91.75   3.818%   $95.253   $95.25   $95.25   $95.30  
  Purchase #2 $161.28   5.649%   $170.3907   $170.39   $170.40   $170.40  
  Purchase #3 $244.92   13.743%   $278.5794   $278.58   $278.60   $278.60  
  Purchase #4 $219.56   12.835%   $247.7405   $247.74   $247.75   $247.70  
  Purchase #5 $21.68   4.518%   $22.6595   $22.66   $22.65   $22.70  
  Purchase #6 $151.94   13.185%   $171.9733   $171.97   $171.95   $172.00  
  Purchase #7 $23.65   3.375%   $24.4482   $24.45   $24.45   $24.40  
  7 purchase totals = $914.78       $1,011.0446   $1,011.04   $1,011.05   $1,011.10