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 $63.75   5.532%   $67.2767   $67.28   $67.30   $67.30  
  Purchase #2 $230.98   13.744%   $262.7259   $262.73   $262.75   $262.70  
  Purchase #3 $235.28   10.201%   $259.2809   $259.28   $259.30   $259.30  
  Purchase #4 $37.59   7.328%   $40.3446   $40.34   $40.35   $40.30  
  Purchase #5 $83.40   8.327%   $90.3447   $90.34   $90.35   $90.30  
  Purchase #6 $192.44   5.815%   $203.6304   $203.63   $203.65   $203.60  
  Purchase #7 $129.50   13.799%   $147.3697   $147.37   $147.35   $147.40  
  7 purchase totals = $972.94       $1,070.9729   $1,070.97   $1,071.05   $1,070.90