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 $83.55   13.251%   $94.6212   $94.62   $94.60   $94.60  
  Purchase #2 $191.63   13.320%   $217.1551   $217.16   $217.15   $217.20  
  Purchase #3 $230.95   4.338%   $240.9686   $240.97   $240.95   $241.00  
  Purchase #4 $25.47   3.558%   $26.3762   $26.38   $26.40   $26.40  
  Purchase #5 $45.45   7.623%   $48.9147   $48.91   $48.90   $48.90  
  Purchase #6 $211.44   3.869%   $219.6206   $219.62   $219.60   $219.60  
  Purchase #7 $151.95   12.705%   $171.2552   $171.26   $171.25   $171.30  
  7 purchase totals = $940.44       $1,018.9116   $1,018.92   $1,018.85   $1,019.00