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 $87.39   8.828%   $95.1048   $95.10   $95.10   $95.10  
  Purchase #2 $212.85   10.636%   $235.4887   $235.49   $235.50   $235.50  
  Purchase #3 $132.70   5.448%   $139.9295   $139.93   $139.95   $139.90  
  Purchase #4 $120.73   11.755%   $134.9218   $134.92   $134.90   $134.90  
  Purchase #5 $44.59   9.142%   $48.6664   $48.67   $48.65   $48.70  
  Purchase #6 $220.30   11.469%   $245.5662   $245.57   $245.55   $245.60  
  Purchase #7 $143.55   9.392%   $157.0322   $157.03   $157.05   $157.00  
  7 purchase totals = $962.11       $1,056.7096   $1,056.71   $1,056.70   $1,056.70