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 $244.94   7.222%   $262.6296   $262.63   $262.65   $262.60  
  Purchase #2 $117.36   7.555%   $126.2265   $126.23   $126.25   $126.20  
  Purchase #3 $123.73   3.107%   $127.5743   $127.57   $127.55   $127.60  
  Purchase #4 $30.42   11.175%   $33.8194   $33.82   $33.80   $33.80  
  Purchase #5 $212.43   6.470%   $226.1742   $226.17   $226.15   $226.20  
  Purchase #6 $39.61   9.266%   $43.2803   $43.28   $43.30   $43.30  
  Purchase #7 $52.36   3.292%   $54.0837   $54.08   $54.10   $54.10  
  7 purchase totals = $820.85       $873.7880   $873.78   $873.80   $873.80