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 $61.43   9.121%   $67.033   $67.03   $67.05   $67.00  
  Purchase #2 $201.51   12.395%   $226.4872   $226.49   $226.50   $226.50  
  Purchase #3 $53.27   10.774%   $59.0093   $59.01   $59.00   $59.00  
  Purchase #4 $12.70   10.699%   $14.0588   $14.06   $14.05   $14.10  
  Purchase #5 $237.97   6.460%   $253.3429   $253.34   $253.35   $253.30  
  Purchase #6 $246.47   12.499%   $277.2763   $277.28   $277.30   $277.30  
  Purchase #7 $210.35   4.498%   $219.8115   $219.81   $219.80   $219.80  
  7 purchase totals = $1,023.70       $1,117.0190   $1,117.02   $1,117.05   $1,117.00