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 $67.85   10.437%   $74.9315   $74.93   $74.95   $74.90  
  Purchase #2 $244.43   13.596%   $277.6627   $277.66   $277.65   $277.70  
  Purchase #3 $175.33   7.546%   $188.5604   $188.56   $188.55   $188.60  
  Purchase #4 $225.37   10.121%   $248.1797   $248.18   $248.20   $248.20  
  Purchase #5 $245.60   6.870%   $262.4727   $262.47   $262.45   $262.50  
  Purchase #6 $23.58   9.685%   $25.8637   $25.86   $25.85   $25.90  
  Purchase #7 $21.77   13.478%   $24.7042   $24.70   $24.70   $24.70  
  7 purchase totals = $1,003.93       $1,102.3749   $1,102.36   $1,102.35   $1,102.50