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 $147.28   4.620%   $154.0843   $154.08   $154.10   $154.10  
  Purchase #2 $92.76   9.623%   $101.6863   $101.69   $101.70   $101.70  
  Purchase #3 $246.61   6.678%   $263.0786   $263.08   $263.10   $263.10  
  Purchase #4 $204.81   7.211%   $219.5788   $219.58   $219.60   $219.60  
  Purchase #5 $33.93   13.415%   $38.4817   $38.48   $38.50   $38.50  
  Purchase #6 $161.96   6.800%   $172.9733   $172.97   $172.95   $173.00  
  Purchase #7 $140.70   7.475%   $151.2173   $151.22   $151.20   $151.20  
  7 purchase totals = $1,028.05       $1,101.1003   $1,101.10   $1,101.15   $1,101.20