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 $60.37   3.417%   $62.4328   $62.43   $62.45   $62.40  
  Purchase #2 $221.76   8.847%   $241.3791   $241.38   $241.40   $241.40  
  Purchase #3 $159.70   11.804%   $178.551   $178.55   $178.55   $178.60  
  Purchase #4 $59.52   3.435%   $61.5645   $61.56   $61.55   $61.60  
  Purchase #5 $232.48   13.520%   $263.9113   $263.91   $263.90   $263.90  
  Purchase #6 $74.46   8.500%   $80.7891   $80.79   $80.80   $80.80  
  Purchase #7 $150.79   8.573%   $163.7172   $163.72   $163.70   $163.70  
  7 purchase totals = $959.08       $1,052.3450   $1,052.34   $1,052.35   $1,052.40