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 $241.49   11.427%   $269.0851   $269.09   $269.10   $269.10  
  Purchase #2 $184.90   8.215%   $200.0895   $200.09   $200.10   $200.10  
  Purchase #3 $34.98   12.430%   $39.328   $39.33   $39.35   $39.30  
  Purchase #4 $212.34   6.820%   $226.8216   $226.82   $226.80   $226.80  
  Purchase #5 $212.67   6.305%   $226.0788   $226.08   $226.10   $226.10  
  Purchase #6 $153.74   8.457%   $166.7418   $166.74   $166.75   $166.70  
  Purchase #7 $74.45   3.495%   $77.052   $77.05   $77.05   $77.10  
  7 purchase totals = $1,114.57       $1,205.1968   $1,205.20   $1,205.25   $1,205.20