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 $48.55   12.552%   $54.644   $54.64   $54.65   $54.60  
  Purchase #2 $79.55   9.123%   $86.8073   $86.81   $86.80   $86.80  
  Purchase #3 $136.53   4.309%   $142.4131   $142.41   $142.40   $142.40  
  Purchase #4 $180.62   12.367%   $202.9573   $202.96   $202.95   $203.00  
  Purchase #5 $152.90   8.373%   $165.7023   $165.70   $165.70   $165.70  
  Purchase #6 $211.84   4.740%   $221.8812   $221.88   $221.90   $221.90  
  Purchase #7 $178.99   4.229%   $186.5595   $186.56   $186.55   $186.60  
  7 purchase totals = $988.98       $1,060.9647   $1,060.96   $1,060.95   $1,061.00