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 $175.28   11.286%   $195.0621   $195.06   $195.05   $195.10  
  Purchase #2 $118.49   3.736%   $122.9168   $122.92   $122.90   $122.90  
  Purchase #3 $64.55   6.859%   $68.9775   $68.98   $69.00   $69.00  
  Purchase #4 $180.98   12.838%   $204.2142   $204.21   $204.20   $204.20  
  Purchase #5 $137.88   8.526%   $149.6356   $149.64   $149.65   $149.60  
  Purchase #6 $130.35   5.505%   $137.5258   $137.53   $137.55   $137.50  
  Purchase #7 $167.47   8.371%   $181.4889   $181.49   $181.50   $181.50  
  7 purchase totals = $975.00       $1,059.8209   $1,059.83   $1,059.85   $1,059.80