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 $65.38   5.314%   $68.8543   $68.85   $68.85   $68.90  
  Purchase #2 $228.87   5.832%   $242.2177   $242.22   $242.20   $242.20  
  Purchase #3 $186.27   6.801%   $198.9382   $198.94   $198.95   $198.90  
  Purchase #4 $198.86   7.166%   $213.1103   $213.11   $213.10   $213.10  
  Purchase #5 $227.58   10.734%   $252.0084   $252.01   $252.00   $252.00  
  Purchase #6 $147.46   13.785%   $167.7874   $167.79   $167.80   $167.80  
  Purchase #7 $48.37   9.194%   $52.8171   $52.82   $52.80   $52.80  
  7 purchase totals = $1,102.79       $1,195.7334   $1,195.74   $1,195.70   $1,195.70