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 $60.35   3.346%   $62.3693   $62.37   $62.35   $62.40  
  Purchase #2 $125.52   9.556%   $137.5147   $137.51   $137.50   $137.50  
  Purchase #3 $130.62   9.709%   $143.3019   $143.30   $143.30   $143.30  
  Purchase #4 $192.57   4.723%   $201.6651   $201.67   $201.65   $201.70  
  Purchase #5 $145.98   6.782%   $155.8804   $155.88   $155.90   $155.90  
  Purchase #6 $238.50   5.328%   $251.2073   $251.21   $251.20   $251.20  
  Purchase #7 $229.36   7.716%   $247.0574   $247.06   $247.05   $247.10  
  7 purchase totals = $1,122.90       $1,198.9961   $1,199.00   $1,198.95   $1,199.10