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 $242.48   9.719%   $266.0466   $266.05   $266.05   $266.00  
  Purchase #2 $22.65   4.440%   $23.6557   $23.66   $23.65   $23.70  
  Purchase #3 $158.28   8.726%   $172.0915   $172.09   $172.10   $172.10  
  Purchase #4 $138.60   12.633%   $156.1093   $156.11   $156.10   $156.10  
  Purchase #5 $216.29   11.170%   $240.4496   $240.45   $240.45   $240.40  
  Purchase #6 $82.46   9.633%   $90.4034   $90.40   $90.40   $90.40  
  Purchase #7 $62.29   6.125%   $66.1053   $66.11   $66.10   $66.10  
  7 purchase totals = $923.05       $1,014.8614   $1,014.87   $1,014.85   $1,014.80