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 $108.31   5.220%   $113.9638   $113.96   $113.95   $114.00  
  Purchase #2 $215.36   5.261%   $226.6901   $226.69   $226.70   $226.70  
  Purchase #3 $29.44   12.502%   $33.1206   $33.12   $33.10   $33.10  
  Purchase #4 $196.99   13.659%   $223.8969   $223.90   $223.90   $223.90  
  Purchase #5 $108.57   6.113%   $115.2069   $115.21   $115.20   $115.20  
  Purchase #6 $183.94   7.824%   $198.3315   $198.33   $198.35   $198.30  
  Purchase #7 $134.81   10.546%   $149.0271   $149.03   $149.05   $149.00  
  7 purchase totals = $977.42       $1,060.2369   $1,060.24   $1,060.25   $1,060.20