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 $214.29   9.669%   $235.0097   $235.01   $235.00   $235.00  
  Purchase #2 $117.37   5.522%   $123.8512   $123.85   $123.85   $123.90  
  Purchase #3 $45.94   6.176%   $48.7773   $48.78   $48.80   $48.80  
  Purchase #4 $140.65   9.657%   $154.2326   $154.23   $154.25   $154.20  
  Purchase #5 $227.82   7.645%   $245.2368   $245.24   $245.25   $245.20  
  Purchase #6 $162.33   7.623%   $174.7044   $174.70   $174.70   $174.70  
  Purchase #7 $126.86   3.159%   $130.8675   $130.87   $130.85   $130.90  
  7 purchase totals = $1,035.26       $1,112.6795   $1,112.68   $1,112.70   $1,112.70