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 $137.73   10.831%   $152.6475   $152.65   $152.65   $152.60  
  Purchase #2 $204.78   3.133%   $211.1958   $211.20   $211.20   $211.20  
  Purchase #3 $179.34   10.267%   $197.7528   $197.75   $197.75   $197.80  
  Purchase #4 $211.46   3.333%   $218.508   $218.51   $218.50   $218.50  
  Purchase #5 $72.69   5.357%   $76.584   $76.58   $76.60   $76.60  
  Purchase #6 $203.58   3.388%   $210.4773   $210.48   $210.50   $210.50  
  Purchase #7 $91.91   6.170%   $97.5808   $97.58   $97.60   $97.60  
  7 purchase totals = $1,101.49       $1,164.7462   $1,164.75   $1,164.80   $1,164.80