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 $236.52   4.316%   $246.7282   $246.73   $246.75   $246.70  
  Purchase #2 $99.28   4.356%   $103.6046   $103.60   $103.60   $103.60  
  Purchase #3 $164.68   10.501%   $181.973   $181.97   $181.95   $182.00  
  Purchase #4 $205.59   3.273%   $212.319   $212.32   $212.30   $212.30  
  Purchase #5 $35.89   3.669%   $37.2068   $37.21   $37.20   $37.20  
  Purchase #6 $170.26   3.386%   $176.025   $176.03   $176.05   $176.00  
  Purchase #7 $86.76   4.343%   $90.528   $90.53   $90.55   $90.50  
  7 purchase totals = $998.98       $1,048.3846   $1,048.39   $1,048.40   $1,048.30