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 $69.35   4.312%   $72.3404   $72.34   $72.35   $72.30  
  Purchase #2 $149.45   4.803%   $156.6281   $156.63   $156.65   $156.60  
  Purchase #3 $62.70   7.264%   $67.2545   $67.25   $67.25   $67.30  
  Purchase #4 $192.36   10.418%   $212.4001   $212.40   $212.40   $212.40  
  Purchase #5 $118.82   6.573%   $126.63   $126.63   $126.65   $126.60  
  Purchase #6 $84.60   9.270%   $92.4424   $92.44   $92.45   $92.40  
  Purchase #7 $29.75   6.670%   $31.7343   $31.73   $31.75   $31.70  
  7 purchase totals = $707.03       $759.4298   $759.42   $759.50   $759.30