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 $59.40   4.620%   $62.1443   $62.14   $62.15   $62.10  
  Purchase #2 $241.82   11.422%   $269.4407   $269.44   $269.45   $269.40  
  Purchase #3 $108.66   7.674%   $116.9986   $117.00   $117.00   $117.00  
  Purchase #4 $127.56   5.274%   $134.2875   $134.29   $134.30   $134.30  
  Purchase #5 $245.68   5.256%   $258.5929   $258.59   $258.60   $258.60  
  Purchase #6 $48.29   7.288%   $51.8094   $51.81   $51.80   $51.80  
  Purchase #7 $211.60   5.760%   $223.7882   $223.79   $223.80   $223.80  
  7 purchase totals = $1,043.01       $1,117.0616   $1,117.06   $1,117.10   $1,117.00