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 $231.26   5.831%   $244.7448   $244.74   $244.75   $244.70  
  Purchase #2 $73.45   10.391%   $81.0822   $81.08   $81.10   $81.10  
  Purchase #3 $126.74   6.377%   $134.8222   $134.82   $134.80   $134.80  
  Purchase #4 $166.25   9.277%   $181.673   $181.67   $181.65   $181.70  
  Purchase #5 $61.92   4.850%   $64.9231   $64.92   $64.90   $64.90  
  Purchase #6 $225.95   11.369%   $251.6383   $251.64   $251.65   $251.60  
  Purchase #7 $125.47   8.322%   $135.9116   $135.91   $135.90   $135.90  
  7 purchase totals = $1,011.04       $1,094.7952   $1,094.78   $1,094.75   $1,094.70