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 $216.94   8.565%   $235.5209   $235.52   $235.50   $235.50  
  Purchase #2 $5.84   12.801%   $6.5876   $6.59   $6.60   $6.60  
  Purchase #3 $226.58   4.563%   $236.9188   $236.92   $236.90   $236.90  
  Purchase #4 $93.93   3.286%   $97.0165   $97.02   $97.00   $97.00  
  Purchase #5 $71.43   7.111%   $76.5094   $76.51   $76.50   $76.50  
  Purchase #6 $191.61   9.332%   $209.491   $209.49   $209.50   $209.50  
  Purchase #7 $211.61   11.196%   $235.3019   $235.30   $235.30   $235.30  
  7 purchase totals = $1,017.94       $1,097.3461   $1,097.35   $1,097.30   $1,097.30