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 $68.62   10.269%   $75.6666   $75.67   $75.65   $75.70  
  Purchase #2 $174.55   10.751%   $193.3159   $193.32   $193.30   $193.30  
  Purchase #3 $226.89   3.565%   $234.9786   $234.98   $235.00   $235.00  
  Purchase #4 $153.32   11.515%   $170.9748   $170.97   $170.95   $171.00  
  Purchase #5 $210.85   12.815%   $237.8704   $237.87   $237.85   $237.90  
  Purchase #6 $147.32   5.676%   $155.6819   $155.68   $155.70   $155.70  
  Purchase #7 $54.63   6.230%   $58.0334   $58.03   $58.05   $58.00  
  7 purchase totals = $1,036.18       $1,126.5216   $1,126.52   $1,126.50   $1,126.60