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 $110.85   3.151%   $114.3429   $114.34   $114.35   $114.30  
  Purchase #2 $62.79   12.304%   $70.5157   $70.52   $70.50   $70.50  
  Purchase #3 $211.96   7.335%   $227.5073   $227.51   $227.50   $227.50  
  Purchase #4 $181.43   12.537%   $204.1759   $204.18   $204.20   $204.20  
  Purchase #5 $57.48   4.379%   $59.997   $60.00   $60.00   $60.00  
  Purchase #6 $147.49   13.446%   $167.3215   $167.32   $167.30   $167.30  
  Purchase #7 $193.84   3.468%   $200.5624   $200.56   $200.55   $200.60  
  7 purchase totals = $965.84       $1,044.4227   $1,044.43   $1,044.40   $1,044.40