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 $60.97   13.241%   $69.043   $69.04   $69.05   $69.00  
  Purchase #2 $182.68   4.317%   $190.5663   $190.57   $190.55   $190.60  
  Purchase #3 $141.48   11.333%   $157.5139   $157.51   $157.50   $157.50  
  Purchase #4 $24.69   9.505%   $27.0368   $27.04   $27.05   $27.00  
  Purchase #5 $147.53   9.417%   $161.4229   $161.42   $161.40   $161.40  
  Purchase #6 $213.82   11.658%   $238.7471   $238.75   $238.75   $238.70  
  Purchase #7 $202.40   8.286%   $219.1709   $219.17   $219.15   $219.20  
  7 purchase totals = $973.57       $1,063.5009   $1,063.50   $1,063.45   $1,063.40