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 $56.82   5.230%   $59.7917   $59.79   $59.80   $59.80  
  Purchase #2 $76.31   12.660%   $85.9708   $85.97   $85.95   $86.00  
  Purchase #3 $220.30   7.235%   $236.2387   $236.24   $236.25   $236.20  
  Purchase #4 $36.35   6.129%   $38.5779   $38.58   $38.60   $38.60  
  Purchase #5 $156.31   4.700%   $163.6566   $163.66   $163.65   $163.70  
  Purchase #6 $206.94   10.606%   $228.8881   $228.89   $228.90   $228.90  
  Purchase #7 $194.82   9.374%   $213.0824   $213.08   $213.10   $213.10  
  7 purchase totals = $947.85       $1,026.2062   $1,026.21   $1,026.25   $1,026.30