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 $222.95   8.462%   $241.816   $241.82   $241.80   $241.80  
  Purchase #2 $62.80   4.102%   $65.3761   $65.38   $65.40   $65.40  
  Purchase #3 $212.79   3.302%   $219.8163   $219.82   $219.80   $219.80  
  Purchase #4 $194.64   10.503%   $215.083   $215.08   $215.10   $215.10  
  Purchase #5 $82.42   6.106%   $87.4526   $87.45   $87.45   $87.50  
  Purchase #6 $87.42   7.728%   $94.1758   $94.18   $94.20   $94.20  
  Purchase #7 $83.57   3.631%   $86.6044   $86.60   $86.60   $86.60  
  7 purchase totals = $946.59       $1,010.3242   $1,010.33   $1,010.35   $1,010.40