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 $196.33   3.763%   $203.7179   $203.72   $203.70   $203.70  
  Purchase #2 $162.68   9.809%   $178.6373   $178.64   $178.65   $178.60  
  Purchase #3 $24.37   5.128%   $25.6197   $25.62   $25.60   $25.60  
  Purchase #4 $87.81   8.563%   $95.3292   $95.33   $95.35   $95.30  
  Purchase #5 $154.84   8.469%   $167.9534   $167.95   $167.95   $168.00  
  Purchase #6 $222.93   4.232%   $232.3644   $232.36   $232.35   $232.40  
  Purchase #7 $124.76   12.778%   $140.7018   $140.70   $140.70   $140.70  
  7 purchase totals = $973.72       $1,044.3237   $1,044.32   $1,044.30   $1,044.30