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 $13.67   6.532%   $14.5629   $14.56   $14.55   $14.60  
  Purchase #2 $120.31   10.438%   $132.868   $132.87   $132.85   $132.90  
  Purchase #3 $106.25   9.416%   $116.2545   $116.25   $116.25   $116.30  
  Purchase #4 $72.30   12.148%   $81.083   $81.08   $81.10   $81.10  
  Purchase #5 $52.85   5.251%   $55.6252   $55.63   $55.65   $55.60  
  Purchase #6 $23.94   8.557%   $25.9885   $25.99   $26.00   $26.00  
  Purchase #7 $35.57   9.309%   $38.8812   $38.88   $38.90   $38.90  
  7 purchase totals = $424.89       $465.2633   $465.26   $465.30   $465.40