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 $216.83   7.361%   $232.7909   $232.79   $232.80   $232.80  
  Purchase #2 $200.29   5.424%   $211.1537   $211.15   $211.15   $211.20  
  Purchase #3 $228.36   10.214%   $251.6847   $251.68   $251.70   $251.70  
  Purchase #4 $49.84   6.508%   $53.0836   $53.08   $53.10   $53.10  
  Purchase #5 $37.47   8.737%   $40.7438   $40.74   $40.75   $40.70  
  Purchase #6 $125.79   10.393%   $138.8634   $138.86   $138.85   $138.90  
  Purchase #7 $121.37   3.482%   $125.5961   $125.60   $125.60   $125.60  
  7 purchase totals = $979.95       $1,053.9162   $1,053.90   $1,053.95   $1,054.00