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 $74.88   3.121%   $77.217   $77.22   $77.20   $77.20  
  Purchase #2 $214.67   12.194%   $240.8469   $240.85   $240.85   $240.80  
  Purchase #3 $145.90   4.207%   $152.038   $152.04   $152.05   $152.00  
  Purchase #4 $203.87   7.310%   $218.7729   $218.77   $218.75   $218.80  
  Purchase #5 $232.99   13.728%   $264.9749   $264.97   $264.95   $265.00  
  Purchase #6 $142.61   3.149%   $147.1008   $147.10   $147.10   $147.10  
  Purchase #7 $89.75   5.207%   $94.4233   $94.42   $94.40   $94.40  
  7 purchase totals = $1,104.67       $1,195.3738   $1,195.37   $1,195.30   $1,195.30