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 $199.32   13.533%   $226.294   $226.29   $226.30   $226.30  
  Purchase #2 $235.36   13.191%   $266.4063   $266.41   $266.40   $266.40  
  Purchase #3 $197.67   7.723%   $212.9361   $212.94   $212.95   $212.90  
  Purchase #4 $148.58   5.226%   $156.3448   $156.34   $156.35   $156.30  
  Purchase #5 $31.97   11.532%   $35.6568   $35.66   $35.65   $35.70  
  Purchase #6 $241.82   11.394%   $269.373   $269.37   $269.35   $269.40  
  Purchase #7 $7.62   5.321%   $8.0255   $8.03   $8.05   $8.00  
  7 purchase totals = $1,062.34       $1,175.0365   $1,175.04   $1,175.05   $1,175.00