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 $62.58   13.581%   $71.079   $71.08   $71.10   $71.10  
  Purchase #2 $177.38   9.125%   $193.5659   $193.57   $193.55   $193.60  
  Purchase #3 $227.87   7.429%   $244.7985   $244.80   $244.80   $244.80  
  Purchase #4 $213.54   13.274%   $241.8853   $241.89   $241.90   $241.90  
  Purchase #5 $61.53   8.356%   $66.6714   $66.67   $66.65   $66.70  
  Purchase #6 $64.82   7.418%   $69.6283   $69.63   $69.65   $69.60  
  Purchase #7 $189.93   11.348%   $211.4833   $211.48   $211.50   $211.50  
  7 purchase totals = $997.65       $1,099.1117   $1,099.12   $1,099.15   $1,099.20