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 $194.89   8.277%   $211.021   $211.02   $211.00   $211.00  
  Purchase #2 $119.60   13.409%   $135.6372   $135.64   $135.65   $135.60  
  Purchase #3 $41.26   5.182%   $43.3981   $43.40   $43.40   $43.40  
  Purchase #4 $179.67   5.614%   $189.7567   $189.76   $189.75   $189.80  
  Purchase #5 $195.45   11.780%   $218.474   $218.47   $218.45   $218.50  
  Purchase #6 $89.85   9.262%   $98.1719   $98.17   $98.15   $98.20  
  Purchase #7 $214.35   7.184%   $229.7489   $229.75   $229.75   $229.70  
  7 purchase totals = $1,035.07       $1,126.2078   $1,126.21   $1,126.15   $1,126.20