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 $115.69   7.209%   $124.0301   $124.03   $124.05   $124.00  
  Purchase #2 $170.58   6.687%   $181.9867   $181.99   $182.00   $182.00  
  Purchase #3 $21.52   7.824%   $23.2037   $23.20   $23.20   $23.20  
  Purchase #4 $124.85   10.621%   $138.1103   $138.11   $138.10   $138.10  
  Purchase #5 $167.64   10.295%   $184.8985   $184.90   $184.90   $184.90  
  Purchase #6 $146.44   9.692%   $160.633   $160.63   $160.65   $160.60  
  Purchase #7 $213.29   10.583%   $235.8625   $235.86   $235.85   $235.90  
  7 purchase totals = $960.01       $1,048.7248   $1,048.72   $1,048.75   $1,048.70