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 $98.33   5.342%   $103.5828   $103.58   $103.60   $103.60  
  Purchase #2 $184.43   5.139%   $193.9079   $193.91   $193.90   $193.90  
  Purchase #3 $67.81   8.161%   $73.344   $73.34   $73.35   $73.30  
  Purchase #4 $130.75   7.333%   $140.3379   $140.34   $140.35   $140.30  
  Purchase #5 $223.53   9.814%   $245.4672   $245.47   $245.45   $245.50  
  Purchase #6 $240.80   11.543%   $268.5955   $268.60   $268.60   $268.60  
  Purchase #7 $95.29   4.106%   $99.2026   $99.20   $99.20   $99.20  
  7 purchase totals = $1,040.94       $1,124.4379   $1,124.44   $1,124.45   $1,124.40