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 $88.26   5.587%   $93.1911   $93.19   $93.20   $93.20  
  Purchase #2 $154.67   3.647%   $160.3108   $160.31   $160.30   $160.30  
  Purchase #3 $128.40   8.163%   $138.8813   $138.88   $138.90   $138.90  
  Purchase #4 $223.26   9.843%   $245.2355   $245.24   $245.25   $245.20  
  Purchase #5 $71.44   4.488%   $74.6462   $74.65   $74.65   $74.60  
  Purchase #6 $213.85   6.762%   $228.3105   $228.31   $228.30   $228.30  
  Purchase #7 $218.82   7.506%   $235.2446   $235.24   $235.25   $235.20  
  7 purchase totals = $1,098.70       $1,175.8200   $1,175.82   $1,175.85   $1,175.70