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 $92.41   12.487%   $103.9492   $103.95   $103.95   $103.90  
  Purchase #2 $192.88   9.615%   $211.4254   $211.43   $211.45   $211.40  
  Purchase #3 $163.88   10.423%   $180.9612   $180.96   $180.95   $181.00  
  Purchase #4 $170.86   11.415%   $190.3637   $190.36   $190.35   $190.40  
  Purchase #5 $176.78   5.751%   $186.9466   $186.95   $186.95   $186.90  
  Purchase #6 $16.28   4.490%   $17.011   $17.01   $17.00   $17.00  
  Purchase #7 $165.51   5.792%   $175.0963   $175.10   $175.10   $175.10  
  7 purchase totals = $978.60       $1,065.7534   $1,065.76   $1,065.75   $1,065.70