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 $174.93   8.700%   $190.1489   $190.15   $190.15   $190.10  
  Purchase #2 $33.82   8.807%   $36.7985   $36.80   $36.80   $36.80  
  Purchase #3 $201.27   9.763%   $220.92   $220.92   $220.90   $220.90  
  Purchase #4 $167.33   5.305%   $176.2069   $176.21   $176.20   $176.20  
  Purchase #5 $236.69   7.217%   $253.7719   $253.77   $253.75   $253.80  
  Purchase #6 $198.41   6.627%   $211.5586   $211.56   $211.55   $211.60  
  Purchase #7 $163.66   7.765%   $176.3682   $176.37   $176.35   $176.40  
  7 purchase totals = $1,176.11       $1,265.7730   $1,265.78   $1,265.70   $1,265.80