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 $212.28   5.643%   $224.259   $224.26   $224.25   $224.30  
  Purchase #2 $94.43   8.413%   $102.3744   $102.37   $102.35   $102.40  
  Purchase #3 $225.41   9.104%   $245.9313   $245.93   $245.95   $245.90  
  Purchase #4 $72.45   6.360%   $77.0578   $77.06   $77.05   $77.10  
  Purchase #5 $173.77   8.307%   $188.2051   $188.21   $188.20   $188.20  
  Purchase #6 $163.51   3.749%   $169.64   $169.64   $169.65   $169.60  
  Purchase #7 $192.70   5.218%   $202.7551   $202.76   $202.75   $202.80  
  7 purchase totals = $1,134.55       $1,210.2227   $1,210.23   $1,210.20   $1,210.30