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 $193.78   10.530%   $214.185   $214.19   $214.20   $214.20  
  Purchase #2 $105.43   12.219%   $118.3125   $118.31   $118.30   $118.30  
  Purchase #3 $212.29   9.699%   $232.88   $232.88   $232.90   $232.90  
  Purchase #4 $189.28   3.316%   $195.5565   $195.56   $195.55   $195.60  
  Purchase #5 $50.75   5.371%   $53.4758   $53.48   $53.50   $53.50  
  Purchase #6 $119.60   9.396%   $130.8376   $130.84   $130.85   $130.80  
  Purchase #7 $119.29   4.495%   $124.6521   $124.65   $124.65   $124.70  
  7 purchase totals = $990.42       $1,069.8995   $1,069.91   $1,069.95   $1,070.00