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 $43.40   6.393%   $46.1746   $46.17   $46.15   $46.20  
  Purchase #2 $244.50   13.112%   $276.5588   $276.56   $276.55   $276.60  
  Purchase #3 $211.59   13.485%   $240.1229   $240.12   $240.10   $240.10  
  Purchase #4 $104.81   13.475%   $118.9331   $118.93   $118.95   $118.90  
  Purchase #5 $196.62   4.197%   $204.8721   $204.87   $204.85   $204.90  
  Purchase #6 $48.48   4.691%   $50.7542   $50.75   $50.75   $50.80  
  Purchase #7 $89.57   6.704%   $95.5748   $95.57   $95.55   $95.60  
  7 purchase totals = $938.97       $1,032.9905   $1,032.97   $1,032.90   $1,033.10