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 $10.53   4.127%   $10.9646   $10.96   $10.95   $11.00  
  Purchase #2 $96.35   7.445%   $103.5233   $103.52   $103.50   $103.50  
  Purchase #3 $130.88   13.492%   $148.5383   $148.54   $148.55   $148.50  
  Purchase #4 $172.77   9.189%   $188.6458   $188.65   $188.65   $188.60  
  Purchase #5 $238.35   6.444%   $253.7093   $253.71   $253.70   $253.70  
  Purchase #6 $60.37   8.699%   $65.6216   $65.62   $65.60   $65.60  
  Purchase #7 $226.74   7.543%   $243.843   $243.84   $243.85   $243.80  
  7 purchase totals = $935.99       $1,014.8459   $1,014.84   $1,014.80   $1,014.70