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 $152.86   9.277%   $167.0408   $167.04   $167.05   $167.00  
  Purchase #2 $110.33   4.808%   $115.6347   $115.63   $115.65   $115.60  
  Purchase #3 $149.74   6.515%   $159.4956   $159.50   $159.50   $159.50  
  Purchase #4 $114.41   10.723%   $126.6782   $126.68   $126.70   $126.70  
  Purchase #5 $196.40   8.222%   $212.548   $212.55   $212.55   $212.50  
  Purchase #6 $177.99   13.813%   $202.5758   $202.58   $202.60   $202.60  
  Purchase #7 $24.89   10.655%   $27.542   $27.54   $27.55   $27.50  
  7 purchase totals = $926.62       $1,011.5151   $1,011.52   $1,011.60   $1,011.40