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 $54.45   12.527%   $61.271   $61.27   $61.25   $61.30  
  Purchase #2 $156.84   9.467%   $171.688   $171.69   $171.70   $171.70  
  Purchase #3 $133.49   9.202%   $145.7737   $145.77   $145.75   $145.80  
  Purchase #4 $102.41   4.727%   $107.2509   $107.25   $107.25   $107.30  
  Purchase #5 $182.41   11.824%   $203.9782   $203.98   $204.00   $204.00  
  Purchase #6 $223.82   4.682%   $234.2993   $234.30   $234.30   $234.30  
  Purchase #7 $173.68   13.560%   $197.231   $197.23   $197.25   $197.20  
  7 purchase totals = $1,027.10       $1,121.4921   $1,121.49   $1,121.50   $1,121.60