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 $119.93   5.163%   $126.122   $126.12   $126.10   $126.10  
  Purchase #2 $56.45   7.362%   $60.6058   $60.61   $60.60   $60.60  
  Purchase #3 $219.66   12.529%   $247.1812   $247.18   $247.20   $247.20  
  Purchase #4 $27.79   3.574%   $28.7832   $28.78   $28.80   $28.80  
  Purchase #5 $228.96   10.427%   $252.8337   $252.83   $252.85   $252.80  
  Purchase #6 $222.85   11.438%   $248.3396   $248.34   $248.35   $248.30  
  Purchase #7 $46.93   6.454%   $49.9589   $49.96   $49.95   $50.00  
  7 purchase totals = $922.57       $1,013.8244   $1,013.82   $1,013.85   $1,013.80