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 $41.33   4.760%   $43.2973   $43.30   $43.30   $43.30  
  Purchase #2 $122.37   12.857%   $138.1031   $138.10   $138.10   $138.10  
  Purchase #3 $162.75   6.485%   $173.3043   $173.30   $173.30   $173.30  
  Purchase #4 $202.92   5.797%   $214.6833   $214.68   $214.70   $214.70  
  Purchase #5 $193.91   4.573%   $202.7775   $202.78   $202.80   $202.80  
  Purchase #6 $180.87   8.168%   $195.6435   $195.64   $195.65   $195.60  
  Purchase #7 $80.57   5.361%   $84.8894   $84.89   $84.90   $84.90  
  7 purchase totals = $984.72       $1,052.6984   $1,052.69   $1,052.75   $1,052.70