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 $164.95   12.426%   $185.4467   $185.45   $185.45   $185.40  
  Purchase #2 $22.99   7.379%   $24.6864   $24.69   $24.70   $24.70  
  Purchase #3 $60.58   11.746%   $67.6957   $67.70   $67.70   $67.70  
  Purchase #4 $89.53   7.503%   $96.2474   $96.25   $96.25   $96.20  
  Purchase #5 $226.42   8.203%   $244.9932   $244.99   $245.00   $245.00  
  Purchase #6 $200.27   5.241%   $210.7662   $210.77   $210.75   $210.80  
  Purchase #7 $211.31   5.635%   $223.2173   $223.22   $223.20   $223.20  
  7 purchase totals = $976.05       $1,053.0529   $1,053.07   $1,053.05   $1,053.00