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 $31.28   13.707%   $35.5675   $35.57   $35.55   $35.60  
  Purchase #2 $223.55   10.494%   $247.0093   $247.01   $247.00   $247.00  
  Purchase #3 $231.50   10.344%   $255.4464   $255.45   $255.45   $255.40  
  Purchase #4 $203.58   12.611%   $229.2535   $229.25   $229.25   $229.30  
  Purchase #5 $134.95   4.543%   $141.0808   $141.08   $141.10   $141.10  
  Purchase #6 $114.97   5.505%   $121.2991   $121.30   $121.30   $121.30  
  Purchase #7 $26.83   9.814%   $29.4631   $29.46   $29.45   $29.50  
  7 purchase totals = $966.66       $1,059.1197   $1,059.12   $1,059.10   $1,059.20