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 $186.38   5.670%   $196.9477   $196.95   $196.95   $196.90  
  Purchase #2 $167.67   13.332%   $190.0238   $190.02   $190.00   $190.00  
  Purchase #3 $41.61   6.148%   $44.1682   $44.17   $44.15   $44.20  
  Purchase #4 $184.30   3.753%   $191.2168   $191.22   $191.20   $191.20  
  Purchase #5 $142.67   6.450%   $151.8722   $151.87   $151.85   $151.90  
  Purchase #6 $64.54   9.301%   $70.5429   $70.54   $70.55   $70.50  
  Purchase #7 $208.40   11.123%   $231.5803   $231.58   $231.60   $231.60  
  7 purchase totals = $995.57       $1,076.3519   $1,076.35   $1,076.30   $1,076.30