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 $195.46   5.864%   $206.9218   $206.92   $206.90   $206.90  
  Purchase #2 $97.56   6.162%   $103.5716   $103.57   $103.55   $103.60  
  Purchase #3 $207.35   5.621%   $219.0051   $219.01   $219.00   $219.00  
  Purchase #4 $187.80   8.138%   $203.0832   $203.08   $203.10   $203.10  
  Purchase #5 $35.34   9.122%   $38.5637   $38.56   $38.55   $38.60  
  Purchase #6 $193.47   13.782%   $220.134   $220.13   $220.15   $220.10  
  Purchase #7 $176.31   5.156%   $185.4005   $185.40   $185.40   $185.40  
  7 purchase totals = $1,093.29       $1,176.6799   $1,176.67   $1,176.65   $1,176.70