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 $86.65   10.331%   $95.6018   $95.60   $95.60   $95.60  
  Purchase #2 $250.93   5.408%   $264.5003   $264.50   $264.50   $264.50  
  Purchase #3 $77.45   11.847%   $86.6255   $86.63   $86.65   $86.60  
  Purchase #4 $207.63   6.413%   $220.9453   $220.95   $220.95   $220.90  
  Purchase #5 $108.41   4.570%   $113.3643   $113.36   $113.35   $113.40  
  Purchase #6 $171.93   5.583%   $181.5289   $181.53   $181.55   $181.50  
  Purchase #7 $91.97   9.539%   $100.743   $100.74   $100.75   $100.70  
  7 purchase totals = $994.97       $1,063.3091   $1,063.31   $1,063.35   $1,063.20