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 $248.50   7.651%   $267.5127   $267.51   $267.50   $267.50  
  Purchase #2 $138.69   9.114%   $151.3302   $151.33   $151.35   $151.30  
  Purchase #3 $68.38   8.296%   $74.0528   $74.05   $74.05   $74.10  
  Purchase #4 $101.46   7.600%   $109.171   $109.17   $109.15   $109.20  
  Purchase #5 $186.81   6.446%   $198.8518   $198.85   $198.85   $198.90  
  Purchase #6 $183.33   10.163%   $201.9618   $201.96   $201.95   $202.00  
  Purchase #7 $184.91   9.251%   $202.016   $202.02   $202.00   $202.00  
  7 purchase totals = $1,112.08       $1,204.8963   $1,204.89   $1,204.85   $1,205.00