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 $204.55   13.494%   $232.152   $232.15   $232.15   $232.20  
  Purchase #2 $114.52   12.331%   $128.6415   $128.64   $128.65   $128.60  
  Purchase #3 $25.57   3.390%   $26.4368   $26.44   $26.45   $26.40  
  Purchase #4 $187.36   10.223%   $206.5138   $206.51   $206.50   $206.50  
  Purchase #5 $205.67   4.204%   $214.3164   $214.32   $214.30   $214.30  
  Purchase #6 $234.62   6.826%   $250.6352   $250.64   $250.65   $250.60  
  Purchase #7 $197.43   4.141%   $205.6056   $205.61   $205.60   $205.60  
  7 purchase totals = $1,169.72       $1,264.3013   $1,264.31   $1,264.30   $1,264.20