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 $68.85   11.188%   $76.5529   $76.55   $76.55   $76.60  
  Purchase #2 $89.26   6.525%   $95.0842   $95.08   $95.10   $95.10  
  Purchase #3 $176.50   8.203%   $190.9783   $190.98   $191.00   $191.00  
  Purchase #4 $113.97   9.208%   $124.4644   $124.46   $124.45   $124.50  
  Purchase #5 $208.29   7.820%   $224.5783   $224.58   $224.60   $224.60  
  Purchase #6 $83.85   3.835%   $87.0656   $87.07   $87.05   $87.10  
  Purchase #7 $204.41   5.350%   $215.3459   $215.35   $215.35   $215.30  
  7 purchase totals = $945.13       $1,014.0696   $1,014.07   $1,014.10   $1,014.20