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 $193.64   7.232%   $207.644   $207.64   $207.65   $207.60  
  Purchase #2 $90.99   8.316%   $98.5567   $98.56   $98.55   $98.60  
  Purchase #3 $115.33   3.463%   $119.3239   $119.32   $119.30   $119.30  
  Purchase #4 $47.89   4.738%   $50.159   $50.16   $50.15   $50.20  
  Purchase #5 $194.72   6.790%   $207.9415   $207.94   $207.95   $207.90  
  Purchase #6 $215.70   7.140%   $231.101   $231.10   $231.10   $231.10  
  Purchase #7 $191.68   7.283%   $205.6401   $205.64   $205.65   $205.60  
  7 purchase totals = $1,049.95       $1,120.3662   $1,120.36   $1,120.35   $1,120.30