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 $44.61   5.567%   $47.0934   $47.09   $47.10   $47.10  
  Purchase #2 $158.37   3.231%   $163.4869   $163.49   $163.50   $163.50  
  Purchase #3 $151.80   10.306%   $167.4445   $167.44   $167.45   $167.40  
  Purchase #4 $230.48   3.524%   $238.6021   $238.60   $238.60   $238.60  
  Purchase #5 $80.48   8.809%   $87.5695   $87.57   $87.55   $87.60  
  Purchase #6 $244.69   13.362%   $277.3855   $277.39   $277.40   $277.40  
  Purchase #7 $43.50   7.510%   $46.7669   $46.77   $46.75   $46.80  
  7 purchase totals = $953.93       $1,028.3488   $1,028.35   $1,028.35   $1,028.40