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 $33.27   3.166%   $34.3233   $34.32   $34.30   $34.30  
  Purchase #2 $188.57   8.501%   $204.6003   $204.60   $204.60   $204.60  
  Purchase #3 $36.58   12.190%   $41.0391   $41.04   $41.05   $41.00  
  Purchase #4 $120.78   3.132%   $124.5628   $124.56   $124.55   $124.60  
  Purchase #5 $240.61   10.670%   $266.2831   $266.28   $266.30   $266.30  
  Purchase #6 $212.35   9.584%   $232.7016   $232.70   $232.70   $232.70  
  Purchase #7 $99.75   7.359%   $107.0906   $107.09   $107.10   $107.10  
  7 purchase totals = $931.91       $1,010.6008   $1,010.59   $1,010.60   $1,010.60