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 $79.68   5.572%   $84.1198   $84.12   $84.10   $84.10  
  Purchase #2 $169.78   3.483%   $175.6934   $175.69   $175.70   $175.70  
  Purchase #3 $211.34   5.159%   $222.243   $222.24   $222.25   $222.20  
  Purchase #4 $96.78   5.465%   $102.069   $102.07   $102.05   $102.10  
  Purchase #5 $152.63   6.155%   $162.0244   $162.02   $162.00   $162.00  
  Purchase #6 $168.46   5.256%   $177.3143   $177.31   $177.30   $177.30  
  Purchase #7 $195.83   4.398%   $204.4426   $204.44   $204.45   $204.40  
  7 purchase totals = $1,074.50       $1,127.9065   $1,127.89   $1,127.85   $1,127.80