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 $94.25   8.229%   $102.0058   $102.01   $102.00   $102.00  
  Purchase #2 $163.62   11.529%   $182.4837   $182.48   $182.50   $182.50  
  Purchase #3 $61.51   9.169%   $67.1499   $67.15   $67.15   $67.10  
  Purchase #4 $149.41   9.274%   $163.2663   $163.27   $163.25   $163.30  
  Purchase #5 $91.50   8.439%   $99.2217   $99.22   $99.20   $99.20  
  Purchase #6 $219.52   9.553%   $240.4907   $240.49   $240.50   $240.50  
  Purchase #7 $202.27   4.152%   $210.6683   $210.67   $210.65   $210.70  
  7 purchase totals = $982.08       $1,065.2864   $1,065.29   $1,065.25   $1,065.30