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 $203.82   5.572%   $215.1769   $215.18   $215.20   $215.20  
  Purchase #2 $62.57   10.307%   $69.0191   $69.02   $69.00   $69.00  
  Purchase #3 $203.33   7.698%   $218.9823   $218.98   $219.00   $219.00  
  Purchase #4 $38.67   13.687%   $43.9628   $43.96   $43.95   $44.00  
  Purchase #5 $239.27   4.352%   $249.683   $249.68   $249.70   $249.70  
  Purchase #6 $245.46   9.539%   $268.8744   $268.87   $268.85   $268.90  
  Purchase #7 $71.91   7.371%   $77.2105   $77.21   $77.20   $77.20  
  7 purchase totals = $1,065.03       $1,142.9090   $1,142.90   $1,142.90   $1,143.00