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 $84.65   12.632%   $95.343   $95.34   $95.35   $95.30  
  Purchase #2 $186.86   5.573%   $197.2737   $197.27   $197.25   $197.30  
  Purchase #3 $76.35   11.509%   $85.1371   $85.14   $85.15   $85.10  
  Purchase #4 $136.75   10.409%   $150.9843   $150.98   $151.00   $151.00  
  Purchase #5 $91.86   3.637%   $95.2009   $95.20   $95.20   $95.20  
  Purchase #6 $173.91   11.409%   $193.7514   $193.75   $193.75   $193.80  
  Purchase #7 $212.70   3.169%   $219.4405   $219.44   $219.45   $219.40  
  7 purchase totals = $963.08       $1,037.1309   $1,037.12   $1,037.15   $1,037.10