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 $174.70   5.743%   $184.733   $184.73   $184.75   $184.70  
  Purchase #2 $94.32   5.873%   $99.8594   $99.86   $99.85   $99.90  
  Purchase #3 $109.28   7.144%   $117.087   $117.09   $117.10   $117.10  
  Purchase #4 $149.62   7.322%   $160.5752   $160.58   $160.60   $160.60  
  Purchase #5 $10.45   8.236%   $11.3107   $11.31   $11.30   $11.30  
  Purchase #6 $216.28   10.736%   $239.4998   $239.50   $239.50   $239.50  
  Purchase #7 $249.33   5.733%   $263.6241   $263.62   $263.60   $263.60  
  7 purchase totals = $1,003.98       $1,076.6892   $1,076.69   $1,076.70   $1,076.70