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 $87.59   8.200%   $94.7724   $94.77   $94.75   $94.80  
  Purchase #2 $37.97   9.463%   $41.5631   $41.56   $41.55   $41.60  
  Purchase #3 $204.54   6.603%   $218.0458   $218.05   $218.05   $218.00  
  Purchase #4 $60.25   8.738%   $65.5146   $65.51   $65.50   $65.50  
  Purchase #5 $233.98   9.863%   $257.0574   $257.06   $257.05   $257.10  
  Purchase #6 $150.98   11.687%   $168.625   $168.63   $168.65   $168.60  
  Purchase #7 $228.50   9.479%   $250.1595   $250.16   $250.15   $250.20  
  7 purchase totals = $1,003.81       $1,095.7378   $1,095.74   $1,095.70   $1,095.80