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 $174.28   4.800%   $182.6454   $182.65   $182.65   $182.60  
  Purchase #2 $114.86   9.367%   $125.6189   $125.62   $125.60   $125.60  
  Purchase #3 $17.77   8.511%   $19.2824   $19.28   $19.30   $19.30  
  Purchase #4 $179.95   12.542%   $202.5193   $202.52   $202.50   $202.50  
  Purchase #5 $88.66   7.353%   $95.1792   $95.18   $95.20   $95.20  
  Purchase #6 $162.62   13.775%   $185.0209   $185.02   $185.00   $185.00  
  Purchase #7 $215.74   4.835%   $226.171   $226.17   $226.15   $226.20  
  7 purchase totals = $953.88       $1,036.4371   $1,036.44   $1,036.40   $1,036.40