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 $34.79   5.794%   $36.8057   $36.81   $36.80   $36.80  
  Purchase #2 $208.71   5.287%   $219.7445   $219.74   $219.75   $219.70  
  Purchase #3 $170.30   3.791%   $176.7561   $176.76   $176.75   $176.80  
  Purchase #4 $79.83   5.167%   $83.9548   $83.95   $83.95   $84.00  
  Purchase #5 $235.50   13.369%   $266.984   $266.98   $267.00   $267.00  
  Purchase #6 $225.68   5.203%   $237.4221   $237.42   $237.40   $237.40  
  Purchase #7 $246.84   6.789%   $263.598   $263.60   $263.60   $263.60  
  7 purchase totals = $1,201.65       $1,285.2652   $1,285.26   $1,285.25   $1,285.30