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 $59.38   3.650%   $61.5474   $61.55   $61.55   $61.50  
  Purchase #2 $206.77   11.771%   $231.1089   $231.11   $231.10   $231.10  
  Purchase #3 $104.44   10.385%   $115.2861   $115.29   $115.30   $115.30  
  Purchase #4 $200.26   12.611%   $225.5148   $225.51   $225.50   $225.50  
  Purchase #5 $232.34   3.288%   $239.9793   $239.98   $240.00   $240.00  
  Purchase #6 $164.60   10.493%   $181.8715   $181.87   $181.85   $181.90  
  Purchase #7 $175.57   3.542%   $181.7887   $181.79   $181.80   $181.80  
  7 purchase totals = $1,143.36       $1,237.0967   $1,237.10   $1,237.10   $1,237.10