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 $181.99   7.143%   $194.9895   $194.99   $195.00   $195.00  
  Purchase #2 $90.29   7.458%   $97.0238   $97.02   $97.00   $97.00  
  Purchase #3 $160.83   6.672%   $171.5606   $171.56   $171.55   $171.60  
  Purchase #4 $85.77   11.805%   $95.8951   $95.90   $95.90   $95.90  
  Purchase #5 $204.39   10.709%   $226.2781   $226.28   $226.30   $226.30  
  Purchase #6 $250.42   13.551%   $284.3544   $284.35   $284.35   $284.40  
  Purchase #7 $179.44   9.155%   $195.8677   $195.87   $195.85   $195.90  
  7 purchase totals = $1,153.13       $1,265.9692   $1,265.97   $1,265.95   $1,266.10