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 $41.86   13.804%   $47.6384   $47.64   $47.65   $47.60  
  Purchase #2 $140.78   8.495%   $152.7393   $152.74   $152.75   $152.70  
  Purchase #3 $243.57   13.843%   $277.2874   $277.29   $277.30   $277.30  
  Purchase #4 $175.75   13.112%   $198.7943   $198.79   $198.80   $198.80  
  Purchase #5 $75.84   13.371%   $85.9806   $85.98   $86.00   $86.00  
  Purchase #6 $231.79   5.731%   $245.0739   $245.07   $245.05   $245.10  
  Purchase #7 $169.45   11.423%   $188.8063   $188.81   $188.80   $188.80  
  7 purchase totals = $1,079.04       $1,196.3202   $1,196.32   $1,196.35   $1,196.30