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 $241.34   5.492%   $254.5944   $254.59   $254.60   $254.60  
  Purchase #2 $46.92   13.190%   $53.1087   $53.11   $53.10   $53.10  
  Purchase #3 $154.39   12.824%   $174.189   $174.19   $174.20   $174.20  
  Purchase #4 $85.26   6.830%   $91.0833   $91.08   $91.10   $91.10  
  Purchase #5 $233.99   4.598%   $244.7489   $244.75   $244.75   $244.70  
  Purchase #6 $128.68   9.338%   $140.6961   $140.70   $140.70   $140.70  
  Purchase #7 $199.90   13.454%   $226.7945   $226.79   $226.80   $226.80  
  7 purchase totals = $1,090.48       $1,185.2149   $1,185.21   $1,185.25   $1,185.20