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 $95.84   10.650%   $106.047   $106.05   $106.05   $106.00  
  Purchase #2 $54.31   4.608%   $56.8126   $56.81   $56.80   $56.80  
  Purchase #3 $143.37   7.421%   $154.0095   $154.01   $154.00   $154.00  
  Purchase #4 $103.47   5.619%   $109.284   $109.28   $109.30   $109.30  
  Purchase #5 $152.94   13.741%   $173.9555   $173.96   $173.95   $174.00  
  Purchase #6 $126.89   6.750%   $135.4551   $135.46   $135.45   $135.50  
  Purchase #7 $13.86   11.580%   $15.465   $15.47   $15.45   $15.50  
  7 purchase totals = $690.68       $751.0287   $751.04   $751.00   $751.10