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 $113.28   10.661%   $125.3568   $125.36   $125.35   $125.40  
  Purchase #2 $231.53   8.686%   $251.6407   $251.64   $251.65   $251.60  
  Purchase #3 $85.31   7.270%   $91.512   $91.51   $91.50   $91.50  
  Purchase #4 $228.32   11.612%   $254.8325   $254.83   $254.85   $254.80  
  Purchase #5 $115.54   4.325%   $120.5371   $120.54   $120.55   $120.50  
  Purchase #6 $107.68   4.786%   $112.8336   $112.83   $112.85   $112.80  
  Purchase #7 $62.28   11.392%   $69.3749   $69.37   $69.35   $69.40  
  7 purchase totals = $943.94       $1,026.0876   $1,026.08   $1,026.10   $1,026.00