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 $90.43   7.212%   $96.9518   $96.95   $96.95   $97.00  
  Purchase #2 $160.61   8.262%   $173.8796   $173.88   $173.90   $173.90  
  Purchase #3 $132.93   8.232%   $143.8728   $143.87   $143.85   $143.90  
  Purchase #4 $186.49   9.410%   $204.0387   $204.04   $204.05   $204.00  
  Purchase #5 $175.26   7.231%   $187.9331   $187.93   $187.95   $187.90  
  Purchase #6 $93.68   10.789%   $103.7871   $103.79   $103.80   $103.80  
  Purchase #7 $136.55   10.840%   $151.352   $151.35   $151.35   $151.40  
  7 purchase totals = $975.95       $1,061.8151   $1,061.81   $1,061.85   $1,061.90