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 $57.78   6.530%   $61.553   $61.55   $61.55   $61.60  
  Purchase #2 $158.62   8.229%   $171.6728   $171.67   $171.65   $171.70  
  Purchase #3 $86.79   7.697%   $93.4702   $93.47   $93.45   $93.50  
  Purchase #4 $44.30   7.610%   $47.6712   $47.67   $47.65   $47.70  
  Purchase #5 $232.91   5.470%   $245.6502   $245.65   $245.65   $245.70  
  Purchase #6 $64.86   11.638%   $72.4084   $72.41   $72.40   $72.40  
  Purchase #7 $100.58   8.173%   $108.8004   $108.80   $108.80   $108.80  
  7 purchase totals = $745.84       $801.2262   $801.22   $801.15   $801.40