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 $160.29   5.860%   $169.683   $169.68   $169.70   $169.70  
  Purchase #2 $38.85   7.631%   $41.8146   $41.81   $41.80   $41.80  
  Purchase #3 $156.80   10.661%   $173.5164   $173.52   $173.50   $173.50  
  Purchase #4 $173.72   10.544%   $192.037   $192.04   $192.05   $192.00  
  Purchase #5 $211.98   7.510%   $227.8997   $227.90   $227.90   $227.90  
  Purchase #6 $30.79   11.531%   $34.3404   $34.34   $34.35   $34.30  
  Purchase #7 $243.90   7.701%   $262.6827   $262.68   $262.70   $262.70  
  7 purchase totals = $1,016.33       $1,101.9738   $1,101.97   $1,102.00   $1,101.90