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 $184.47   6.633%   $196.7059   $196.71   $196.70   $196.70  
  Purchase #2 $194.53   9.825%   $213.6426   $213.64   $213.65   $213.60  
  Purchase #3 $163.48   10.701%   $180.974   $180.97   $180.95   $181.00  
  Purchase #4 $225.26   10.667%   $249.2885   $249.29   $249.30   $249.30  
  Purchase #5 $85.40   6.154%   $90.6555   $90.66   $90.65   $90.70  
  Purchase #6 $105.26   5.433%   $110.9788   $110.98   $111.00   $111.00  
  Purchase #7 $142.65   6.737%   $152.2603   $152.26   $152.25   $152.30  
  7 purchase totals = $1,101.05       $1,194.5056   $1,194.51   $1,194.50   $1,194.60