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 $156.52   12.186%   $175.5935   $175.59   $175.60   $175.60  
  Purchase #2 $186.56   4.235%   $194.4608   $194.46   $194.45   $194.50  
  Purchase #3 $46.76   6.396%   $49.7508   $49.75   $49.75   $49.80  
  Purchase #4 $226.36   7.190%   $242.6353   $242.64   $242.65   $242.60  
  Purchase #5 $180.58   3.582%   $187.0484   $187.05   $187.05   $187.00  
  Purchase #6 $144.59   11.424%   $161.108   $161.11   $161.10   $161.10  
  Purchase #7 $124.96   10.511%   $138.0945   $138.09   $138.10   $138.10  
  7 purchase totals = $1,066.33       $1,148.6913   $1,148.69   $1,148.70   $1,148.70