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 $32.52   3.490%   $33.6549   $33.65   $33.65   $33.70  
  Purchase #2 $88.86   4.767%   $93.096   $93.10   $93.10   $93.10  
  Purchase #3 $198.82   4.762%   $208.2878   $208.29   $208.30   $208.30  
  Purchase #4 $241.67   3.705%   $250.6239   $250.62   $250.60   $250.60  
  Purchase #5 $244.72   13.548%   $277.8747   $277.87   $277.85   $277.90  
  Purchase #6 $5.40   5.799%   $5.7131   $5.71   $5.70   $5.70  
  Purchase #7 $235.55   3.367%   $243.481   $243.48   $243.50   $243.50  
  7 purchase totals = $1,047.54       $1,112.7314   $1,112.72   $1,112.70   $1,112.80