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 $68.62   3.628%   $71.1095   $71.11   $71.10   $71.10  
  Purchase #2 $147.38   5.739%   $155.8381   $155.84   $155.85   $155.80  
  Purchase #3 $121.62   7.555%   $130.8084   $130.81   $130.80   $130.80  
  Purchase #4 $246.55   6.828%   $263.3844   $263.38   $263.40   $263.40  
  Purchase #5 $73.44   4.197%   $76.5223   $76.52   $76.50   $76.50  
  Purchase #6 $182.33   10.861%   $202.1329   $202.13   $202.15   $202.10  
  Purchase #7 $199.85   7.323%   $214.485   $214.49   $214.50   $214.50  
  7 purchase totals = $1,039.79       $1,114.2806   $1,114.28   $1,114.30   $1,114.20