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 $142.61   7.261%   $152.9649   $152.96   $152.95   $153.00  
  Purchase #2 $233.35   7.270%   $250.3145   $250.31   $250.30   $250.30  
  Purchase #3 $216.40   6.720%   $230.9421   $230.94   $230.95   $230.90  
  Purchase #4 $230.29   11.647%   $257.1119   $257.11   $257.10   $257.10  
  Purchase #5 $194.30   8.379%   $210.5804   $210.58   $210.60   $210.60  
  Purchase #6 $32.63   6.242%   $34.6668   $34.67   $34.65   $34.70  
  Purchase #7 $216.48   10.744%   $239.7386   $239.74   $239.75   $239.70  
  7 purchase totals = $1,266.06       $1,376.3192   $1,376.31   $1,376.30   $1,376.30