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 $51.26   10.874%   $56.834   $56.83   $56.85   $56.80  
  Purchase #2 $220.87   6.180%   $234.5198   $234.52   $234.50   $234.50  
  Purchase #3 $236.66   11.673%   $264.2853   $264.29   $264.30   $264.30  
  Purchase #4 $92.92   5.300%   $97.8448   $97.84   $97.85   $97.80  
  Purchase #5 $227.88   12.170%   $255.613   $255.61   $255.60   $255.60  
  Purchase #6 $157.57   3.226%   $162.6532   $162.65   $162.65   $162.70  
  Purchase #7 $120.57   7.422%   $129.5187   $129.52   $129.50   $129.50  
  7 purchase totals = $1,107.73       $1,201.2688   $1,201.26   $1,201.25   $1,201.20