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 $194.28   8.617%   $211.0211   $211.02   $211.00   $211.00  
  Purchase #2 $73.47   3.303%   $75.8967   $75.90   $75.90   $75.90  
  Purchase #3 $191.32   3.422%   $197.867   $197.87   $197.85   $197.90  
  Purchase #4 $10.57   11.326%   $11.7672   $11.77   $11.75   $11.80  
  Purchase #5 $27.96   11.360%   $31.1363   $31.14   $31.15   $31.10  
  Purchase #6 $211.80   6.451%   $225.4632   $225.46   $225.45   $225.50  
  Purchase #7 $239.79   12.495%   $269.7518   $269.75   $269.75   $269.80  
  7 purchase totals = $949.19       $1,022.9033   $1,022.91   $1,022.85   $1,023.00