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 $214.59   10.597%   $237.3301   $237.33   $237.35   $237.30  
  Purchase #2 $212.41   7.298%   $227.9117   $227.91   $227.90   $227.90  
  Purchase #3 $103.75   7.180%   $111.1993   $111.20   $111.20   $111.20  
  Purchase #4 $57.95   9.366%   $63.3776   $63.38   $63.40   $63.40  
  Purchase #5 $189.42   5.627%   $200.0787   $200.08   $200.10   $200.10  
  Purchase #6 $113.26   6.547%   $120.6751   $120.68   $120.70   $120.70  
  Purchase #7 $64.84   10.873%   $71.8901   $71.89   $71.90   $71.90  
  7 purchase totals = $956.22       $1,032.4626   $1,032.47   $1,032.55   $1,032.50