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 $43.77   9.827%   $48.0713   $48.07   $48.05   $48.10  
  Purchase #2 $211.51   8.222%   $228.9004   $228.90   $228.90   $228.90  
  Purchase #3 $196.68   7.687%   $211.7988   $211.80   $211.80   $211.80  
  Purchase #4 $60.94   3.414%   $63.0205   $63.02   $63.00   $63.00  
  Purchase #5 $66.30   7.310%   $71.1465   $71.15   $71.15   $71.10  
  Purchase #6 $214.83   4.753%   $225.0409   $225.04   $225.05   $225.00  
  Purchase #7 $200.60   7.632%   $215.9098   $215.91   $215.90   $215.90  
  7 purchase totals = $994.63       $1,063.8882   $1,063.89   $1,063.85   $1,063.80