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 $53.77   11.465%   $59.9347   $59.93   $59.95   $59.90  
  Purchase #2 $197.67   8.860%   $215.1836   $215.18   $215.20   $215.20  
  Purchase #3 $33.97   3.873%   $35.2857   $35.29   $35.30   $35.30  
  Purchase #4 $186.51   8.450%   $202.2701   $202.27   $202.25   $202.30  
  Purchase #5 $198.74   7.700%   $214.043   $214.04   $214.05   $214.00  
  Purchase #6 $182.80   6.672%   $194.9964   $195.00   $195.00   $195.00  
  Purchase #7 $153.83   13.624%   $174.7878   $174.79   $174.80   $174.80  
  7 purchase totals = $1,007.29       $1,096.5013   $1,096.50   $1,096.55   $1,096.50