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 $193.82   6.310%   $206.05   $206.05   $206.05   $206.10  
  Purchase #2 $62.33   5.826%   $65.9613   $65.96   $65.95   $66.00  
  Purchase #3 $174.74   7.569%   $187.9661   $187.97   $187.95   $188.00  
  Purchase #4 $250.54   12.549%   $281.9803   $281.98   $282.00   $282.00  
  Purchase #5 $156.28   7.801%   $168.4714   $168.47   $168.45   $168.50  
  Purchase #6 $188.81   4.737%   $197.7539   $197.75   $197.75   $197.80  
  Purchase #7 $206.51   5.865%   $218.6218   $218.62   $218.60   $218.60  
  7 purchase totals = $1,233.03       $1,326.8048   $1,326.80   $1,326.75   $1,327.00