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 $41.33   12.123%   $46.3404   $46.34   $46.35   $46.30  
  Purchase #2 $212.74   13.732%   $241.9535   $241.95   $241.95   $242.00  
  Purchase #3 $120.68   5.237%   $127   $127.00   $127.00   $127.00  
  Purchase #4 $178.55   3.432%   $184.6778   $184.68   $184.70   $184.70  
  Purchase #5 $208.39   4.469%   $217.7029   $217.70   $217.70   $217.70  
  Purchase #6 $87.68   5.872%   $92.8286   $92.83   $92.85   $92.80  
  Purchase #7 $176.71   12.753%   $199.2458   $199.25   $199.25   $199.20  
  7 purchase totals = $1,026.08       $1,109.7490   $1,109.75   $1,109.80   $1,109.70