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 $43.98   6.705%   $46.9289   $46.93   $46.95   $46.90  
  Purchase #2 $197.94   11.744%   $221.1861   $221.19   $221.20   $221.20  
  Purchase #3 $39.76   6.805%   $42.4657   $42.47   $42.45   $42.50  
  Purchase #4 $141.61   10.528%   $156.5187   $156.52   $156.50   $156.50  
  Purchase #5 $225.80   7.746%   $243.2905   $243.29   $243.30   $243.30  
  Purchase #6 $162.47   13.198%   $183.9128   $183.91   $183.90   $183.90  
  Purchase #7 $129.85   8.458%   $140.8327   $140.83   $140.85   $140.80  
  7 purchase totals = $941.41       $1,035.1354   $1,035.14   $1,035.15   $1,035.10