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 $185.30   9.577%   $203.0462   $203.05   $203.05   $203.00  
  Purchase #2 $126.62   5.514%   $133.6018   $133.60   $133.60   $133.60  
  Purchase #3 $216.59   9.522%   $237.2137   $237.21   $237.20   $237.20  
  Purchase #4 $230.80   3.395%   $238.6357   $238.64   $238.65   $238.60  
  Purchase #5 $185.80   3.592%   $192.4739   $192.47   $192.45   $192.50  
  Purchase #6 $25.56   3.861%   $26.5469   $26.55   $26.55   $26.50  
  Purchase #7 $25.85   11.477%   $28.8168   $28.82   $28.80   $28.80  
  7 purchase totals = $996.52       $1,060.3350   $1,060.34   $1,060.30   $1,060.20