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 $106.52   6.278%   $113.2073   $113.21   $113.20   $113.20  
  Purchase #2 $178.67   12.822%   $201.5791   $201.58   $201.60   $201.60  
  Purchase #3 $23.61   3.660%   $24.4741   $24.47   $24.45   $24.50  
  Purchase #4 $103.54   7.405%   $111.2071   $111.21   $111.20   $111.20  
  Purchase #5 $194.46   4.690%   $203.5802   $203.58   $203.60   $203.60  
  Purchase #6 $165.83   3.154%   $171.0603   $171.06   $171.05   $171.10  
  Purchase #7 $250.93   7.516%   $269.7899   $269.79   $269.80   $269.80  
  7 purchase totals = $1,023.56       $1,094.8980   $1,094.90   $1,094.90   $1,095.00