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 $41.64   3.547%   $43.117   $43.12   $43.10   $43.10  
  Purchase #2 $57.99   8.296%   $62.8009   $62.80   $62.80   $62.80  
  Purchase #3 $54.85   8.814%   $59.6845   $59.68   $59.70   $59.70  
  Purchase #4 $108.30   12.747%   $122.105   $122.11   $122.10   $122.10  
  Purchase #5 $232.56   13.124%   $263.0812   $263.08   $263.10   $263.10  
  Purchase #6 $153.52   6.390%   $163.3299   $163.33   $163.35   $163.30  
  Purchase #7 $160.61   9.304%   $175.5532   $175.55   $175.55   $175.60  
  7 purchase totals = $809.47       $889.6717   $889.67   $889.70   $889.70