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 $85.47   9.358%   $93.4683   $93.47   $93.45   $93.50  
  Purchase #2 $203.76   10.518%   $225.1915   $225.19   $225.20   $225.20  
  Purchase #3 $82.52   4.185%   $85.9735   $85.97   $85.95   $86.00  
  Purchase #4 $151.59   10.622%   $167.6919   $167.69   $167.70   $167.70  
  Purchase #5 $198.99   10.654%   $220.1904   $220.19   $220.20   $220.20  
  Purchase #6 $226.35   9.470%   $247.7853   $247.79   $247.80   $247.80  
  Purchase #7 $65.43   9.627%   $71.7289   $71.73   $71.75   $71.70  
  7 purchase totals = $1,014.11       $1,112.0298   $1,112.03   $1,112.05   $1,112.10