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 $216.93   5.850%   $229.6204   $229.62   $229.60   $229.60  
  Purchase #2 $186.94   11.181%   $207.8418   $207.84   $207.85   $207.80  
  Purchase #3 $141.97   9.732%   $155.7865   $155.79   $155.80   $155.80  
  Purchase #4 $67.64   7.858%   $72.9552   $72.96   $72.95   $73.00  
  Purchase #5 $60.45   11.373%   $67.325   $67.33   $67.35   $67.30  
  Purchase #6 $83.49   10.219%   $92.0218   $92.02   $92.00   $92.00  
  Purchase #7 $191.57   8.816%   $208.4588   $208.46   $208.45   $208.50  
  7 purchase totals = $948.99       $1,034.0095   $1,034.02   $1,034.00   $1,034.00