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 $53.94   9.270%   $58.9402   $58.94   $58.95   $58.90  
  Purchase #2 $226.97   3.357%   $234.5894   $234.59   $234.60   $234.60  
  Purchase #3 $180.98   12.163%   $202.9926   $202.99   $203.00   $203.00  
  Purchase #4 $62.62   5.322%   $65.9526   $65.95   $65.95   $66.00  
  Purchase #5 $101.37   5.594%   $107.0406   $107.04   $107.05   $107.00  
  Purchase #6 $140.35   13.107%   $158.7457   $158.75   $158.75   $158.70  
  Purchase #7 $189.52   5.704%   $200.3302   $200.33   $200.35   $200.30  
  7 purchase totals = $955.75       $1,028.5913   $1,028.59   $1,028.65   $1,028.50