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 $87.65   7.582%   $94.2956   $94.30   $94.30   $94.30  
  Purchase #2 $229.95   12.790%   $259.3606   $259.36   $259.35   $259.40  
  Purchase #3 $196.58   13.429%   $222.9787   $222.98   $223.00   $223.00  
  Purchase #4 $24.92   3.537%   $25.8014   $25.80   $25.80   $25.80  
  Purchase #5 $10.61   12.818%   $11.97   $11.97   $11.95   $12.00  
  Purchase #6 $49.96   7.756%   $53.8349   $53.83   $53.85   $53.80  
  Purchase #7 $82.79   13.301%   $93.8019   $93.80   $93.80   $93.80  
  7 purchase totals = $682.46       $762.0431   $762.04   $762.05   $762.10