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 $87.34   6.532%   $93.045   $93.05   $93.05   $93.00  
  Purchase #2 $174.58   12.178%   $195.8404   $195.84   $195.85   $195.80  
  Purchase #3 $242.87   8.109%   $262.5643   $262.56   $262.55   $262.60  
  Purchase #4 $227.35   7.618%   $244.6695   $244.67   $244.65   $244.70  
  Purchase #5 $232.67   7.644%   $250.4553   $250.46   $250.45   $250.50  
  Purchase #6 $108.85   4.793%   $114.0672   $114.07   $114.05   $114.10  
  Purchase #7 $223.85   7.713%   $241.1156   $241.12   $241.10   $241.10  
  7 purchase totals = $1,297.51       $1,401.7573   $1,401.77   $1,401.70   $1,401.80