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 $228.94   6.567%   $243.9745   $243.97   $243.95   $244.00  
  Purchase #2 $189.82   11.288%   $211.2469   $211.25   $211.25   $211.20  
  Purchase #3 $22.96   6.588%   $24.4726   $24.47   $24.45   $24.50  
  Purchase #4 $223.77   5.221%   $235.453   $235.45   $235.45   $235.50  
  Purchase #5 $244.49   3.420%   $252.8516   $252.85   $252.85   $252.90  
  Purchase #6 $153.41   13.481%   $174.0912   $174.09   $174.10   $174.10  
  Purchase #7 $198.45   9.695%   $217.6897   $217.69   $217.70   $217.70  
  7 purchase totals = $1,261.84       $1,359.7795   $1,359.77   $1,359.75   $1,359.90