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 $152.82   9.611%   $167.5075   $167.51   $167.50   $167.50  
  Purchase #2 $244.99   9.229%   $267.6001   $267.60   $267.60   $267.60  
  Purchase #3 $179.55   13.196%   $203.2434   $203.24   $203.25   $203.20  
  Purchase #4 $172.92   3.491%   $178.9566   $178.96   $178.95   $179.00  
  Purchase #5 $9.58   8.660%   $10.4096   $10.41   $10.40   $10.40  
  Purchase #6 $239.36   7.592%   $257.5322   $257.53   $257.55   $257.50  
  Purchase #7 $36.85   11.250%   $40.9956   $41.00   $41.00   $41.00  
  7 purchase totals = $1,036.07       $1,126.2450   $1,126.25   $1,126.25   $1,126.20