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 $184.77   11.844%   $206.6542   $206.65   $206.65   $206.70  
  Purchase #2 $188.94   6.614%   $201.4365   $201.44   $201.45   $201.40  
  Purchase #3 $70.88   5.568%   $74.8266   $74.83   $74.85   $74.80  
  Purchase #4 $99.56   5.771%   $105.3056   $105.31   $105.30   $105.30  
  Purchase #5 $241.28   8.682%   $262.2279   $262.23   $262.25   $262.20  
  Purchase #6 $235.76   3.409%   $243.7971   $243.80   $243.80   $243.80  
  Purchase #7 $47.95   8.825%   $52.1816   $52.18   $52.20   $52.20  
  7 purchase totals = $1,069.14       $1,146.4295   $1,146.44   $1,146.50   $1,146.40