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 $62.92   11.256%   $70.0023   $70.00   $70.00   $70.00  
  Purchase #2 $53.94   3.282%   $55.7103   $55.71   $55.70   $55.70  
  Purchase #3 $130.73   4.585%   $136.724   $136.72   $136.70   $136.70  
  Purchase #4 $194.35   4.215%   $202.5419   $202.54   $202.55   $202.50  
  Purchase #5 $160.92   3.616%   $166.7389   $166.74   $166.75   $166.70  
  Purchase #6 $221.78   11.769%   $247.8813   $247.88   $247.90   $247.90  
  Purchase #7 $200.46   13.219%   $226.9588   $226.96   $226.95   $227.00  
  7 purchase totals = $1,025.10       $1,106.5575   $1,106.55   $1,106.55   $1,106.50