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 $57.97   7.240%   $62.167   $62.17   $62.15   $62.20  
  Purchase #2 $116.70   6.347%   $124.1069   $124.11   $124.10   $124.10  
  Purchase #3 $247.36   3.164%   $255.1865   $255.19   $255.20   $255.20  
  Purchase #4 $127.32   4.270%   $132.7566   $132.76   $132.75   $132.80  
  Purchase #5 $184.45   8.652%   $200.4086   $200.41   $200.40   $200.40  
  Purchase #6 $181.41   4.271%   $189.158   $189.16   $189.15   $189.20  
  Purchase #7 $170.92   4.306%   $178.2798   $178.28   $178.30   $178.30  
  7 purchase totals = $1,086.13       $1,142.0634   $1,142.08   $1,142.05   $1,142.20