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 $88.37   8.250%   $95.6605   $95.66   $95.65   $95.70  
  Purchase #2 $221.66   9.621%   $242.9859   $242.99   $243.00   $243.00  
  Purchase #3 $72.55   6.197%   $77.0459   $77.05   $77.05   $77.00  
  Purchase #4 $114.64   7.746%   $123.52   $123.52   $123.50   $123.50  
  Purchase #5 $147.31   13.690%   $167.4767   $167.48   $167.50   $167.50  
  Purchase #6 $203.49   6.743%   $217.2113   $217.21   $217.20   $217.20  
  Purchase #7 $121.48   8.419%   $131.7074   $131.71   $131.70   $131.70  
  7 purchase totals = $969.50       $1,055.6077   $1,055.62   $1,055.60   $1,055.60