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 $75.52   13.847%   $85.9773   $85.98   $86.00   $86.00  
  Purchase #2 $186.54   13.373%   $211.486   $211.49   $211.50   $211.50  
  Purchase #3 $189.92   6.817%   $202.8668   $202.87   $202.85   $202.90  
  Purchase #4 $58.64   8.667%   $63.7223   $63.72   $63.70   $63.70  
  Purchase #5 $7.73   3.405%   $7.9932   $7.99   $8.00   $8.00  
  Purchase #6 $238.31   9.492%   $260.9304   $260.93   $260.95   $260.90  
  Purchase #7 $38.48   13.671%   $43.7406   $43.74   $43.75   $43.70  
  7 purchase totals = $795.14       $876.7166   $876.72   $876.75   $876.70