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 $126.30   4.135%   $131.5225   $131.52   $131.50   $131.50  
  Purchase #2 $177.28   5.278%   $186.6368   $186.64   $186.65   $186.60  
  Purchase #3 $60.77   8.630%   $66.0145   $66.01   $66.00   $66.00  
  Purchase #4 $68.35   8.150%   $73.9205   $73.92   $73.90   $73.90  
  Purchase #5 $198.59   6.136%   $210.7755   $210.78   $210.80   $210.80  
  Purchase #6 $211.48   3.642%   $219.1821   $219.18   $219.20   $219.20  
  Purchase #7 $177.89   5.677%   $187.9888   $187.99   $188.00   $188.00  
  7 purchase totals = $1,020.66       $1,076.0407   $1,076.04   $1,076.05   $1,076.00