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 $52.81   7.722%   $56.888   $56.89   $56.90   $56.90  
  Purchase #2 $159.36   11.142%   $177.1159   $177.12   $177.10   $177.10  
  Purchase #3 $72.35   11.522%   $80.6862   $80.69   $80.70   $80.70  
  Purchase #4 $87.35   10.474%   $96.499   $96.50   $96.50   $96.50  
  Purchase #5 $194.87   7.759%   $209.99   $209.99   $210.00   $210.00  
  Purchase #6 $238.76   3.329%   $246.7083   $246.71   $246.70   $246.70  
  Purchase #7 $238.78   4.173%   $248.7443   $248.74   $248.75   $248.70  
  7 purchase totals = $1,044.28       $1,116.6317   $1,116.64   $1,116.65   $1,116.60