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 $181.99   11.297%   $202.5494   $202.55   $202.55   $202.50  
  Purchase #2 $128.66   13.556%   $146.1011   $146.10   $146.10   $146.10  
  Purchase #3 $133.59   10.491%   $147.6049   $147.60   $147.60   $147.60  
  Purchase #4 $157.75   12.380%   $177.2795   $177.28   $177.30   $177.30  
  Purchase #5 $192.87   3.392%   $199.4122   $199.41   $199.40   $199.40  
  Purchase #6 $216.57   11.707%   $241.9238   $241.92   $241.90   $241.90  
  Purchase #7 $86.72   10.459%   $95.79   $95.79   $95.80   $95.80  
  7 purchase totals = $1,098.15       $1,210.6609   $1,210.65   $1,210.65   $1,210.60