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 $61.81   8.475%   $67.0484   $67.05   $67.05   $67.00  
  Purchase #2 $78.99   12.200%   $88.6268   $88.63   $88.65   $88.60  
  Purchase #3 $192.86   10.334%   $212.7902   $212.79   $212.80   $212.80  
  Purchase #4 $245.33   7.219%   $263.0404   $263.04   $263.05   $263.00  
  Purchase #5 $50.85   6.863%   $54.3398   $54.34   $54.35   $54.30  
  Purchase #6 $235.91   11.571%   $263.2071   $263.21   $263.20   $263.20  
  Purchase #7 $57.52   8.435%   $62.3718   $62.37   $62.35   $62.40  
  7 purchase totals = $923.27       $1,011.4245   $1,011.43   $1,011.45   $1,011.30