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 $184.48   9.443%   $201.9004   $201.90   $201.90   $201.90  
  Purchase #2 $216.34   11.519%   $241.2602   $241.26   $241.25   $241.30  
  Purchase #3 $207.67   9.147%   $226.6656   $226.67   $226.65   $226.70  
  Purchase #4 $67.98   7.412%   $73.0187   $73.02   $73.00   $73.00  
  Purchase #5 $219.49   13.838%   $249.863   $249.86   $249.85   $249.90  
  Purchase #6 $238.92   10.546%   $264.1165   $264.12   $264.10   $264.10  
  Purchase #7 $95.50   11.480%   $106.4634   $106.46   $106.45   $106.50  
  7 purchase totals = $1,230.38       $1,363.2878   $1,363.29   $1,363.20   $1,363.40