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 $53.31   12.804%   $60.1358   $60.14   $60.15   $60.10  
  Purchase #2 $203.78   4.626%   $213.2069   $213.21   $213.20   $213.20  
  Purchase #3 $172.57   7.796%   $186.0236   $186.02   $186.00   $186.00  
  Purchase #4 $221.65   13.283%   $251.0918   $251.09   $251.10   $251.10  
  Purchase #5 $218.69   12.592%   $246.2274   $246.23   $246.25   $246.20  
  Purchase #6 $65.95   6.861%   $70.4748   $70.47   $70.45   $70.50  
  Purchase #7 $64.96   4.714%   $68.0222   $68.02   $68.00   $68.00  
  7 purchase totals = $1,000.91       $1,095.1825   $1,095.18   $1,095.15   $1,095.10