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 $186.48   4.762%   $195.3602   $195.36   $195.35   $195.40  
  Purchase #2 $198.56   6.767%   $211.9966   $212.00   $212.00   $212.00  
  Purchase #3 $58.72   5.659%   $62.043   $62.04   $62.05   $62.00  
  Purchase #4 $231.91   7.845%   $250.1033   $250.10   $250.10   $250.10  
  Purchase #5 $242.47   6.363%   $257.8984   $257.90   $257.90   $257.90  
  Purchase #6 $246.56   12.348%   $277.0052   $277.01   $277.00   $277.00  
  Purchase #7 $116.97   11.470%   $130.3865   $130.39   $130.40   $130.40  
  7 purchase totals = $1,281.67       $1,384.7932   $1,384.80   $1,384.80   $1,384.80